In a large, sterile-looking room, the walls are lined with cryogenic chambers, and the floor swirls with freezing mists. Sgt. Kracauer watches as guards lead a group of mercenaries into the room. He congratulates them on being chosen as part of an elite mercenary group. When Zed, one of the mercenaries, complains that they were tricked, Sgt. Kracauer informs him that a man named Kane has paid for them. When Zed protests further, Kracauer insults him and shoves him to the ground. Zed catches himself on a vat of liquid nitrogen, and clutches his hand in pain from the freezing cold.
When Sgt. Kracauer gives the order for the mercenaries to be frozen in the chambers, Zed attempts to escape. He grabs a gun from one of the guards. He engages in a brief firefight with the other guards, then escapes through a doorway. Kracauer orders the guards not to pursue, because Zed has entered the restricted zone, where he is as good as dead.
Zed enters another room, where he is startled to find an old man sculpting a large block of ice. Distracted by the man, he stumbles and drops his gun into another vat. He hesitates, unable to retrieve the gun. Another hand reaches directly into the vat, pulling out the weapon. It is Kane. He hands the gun back to Zed, who burns himself on the frozen metal. He drops it and it shatters. Kane reaches out and touches Zed's face. Kane's touch is so freezing that after only a few seconds Zed collapses, dead. Kane calmly pulls on a pair of gloves, telling the artist to pay no attention to the incident, and to continue his work.
In the TARDIS console room, the scanner shows a world that appears entirely uninhabited, except for a huge, crystalline complex on one side of the planet. The Doctor tells Mel that it is Iceworld, located on the dark side of the planet Svartos. It is a waystation for space travelers. He explains that he has been picking up tracking signals, and that something interesting is happening there.
The TARDIS arrives in a display room for refrigeration units. After looking around briefly, the Doctor and Mel enter a restaurant. As they sit at a table, they overhear the waitress arguing with a customer, who turns out to be their old acquaintance Sabalom Glitz, the space rogue. Glitz asks the Doctor and Mel for their help. When the Doctor is suspicious, Glitz explains that he is trying to deliver secret documents, which other parties are attempting to take from him. When Officer Belazs leads troops to Glitz' table, Mel jumps to his defense. Belazs laughs and explains that she is looking for Glitz because he sold Kane a freighter full of rotten fruit. Glitz, unfortunately, lost the money in a card game. Belazs reveals that it was Glitz who sold his mercenary crew to Kane, but that money is already gone. Belazs informs him that he has 72 hours to come up with the money, or they will confiscate his ship, the Nosferatu. Glitz asks the Doctor again for his help, but the Doctor pulls out a book and turns away in disgust.
In the cryogenic room, the remaining mercenaries are finishing the freezing process. Sgt. Kracauer warns Kane that they were not willing volunteers and that he will have trouble with them when they emerge. Kane dismisses the concern, explaining that the cryogenic process removes all of the memories of the subject. When he revives his mercenary army, they will have no knowledge of their past lives or how they arrived there, and they will be completely dependent on and loyal to Kane.
Back in the restaurant, the manager instructs the waitress who was arguing with Glitz earlier to do as she is told. As she leaves to serve drinks to the customers, she mutters under her breath that she hopes the dragon gets him. Mel overhears this, and the waitress, Ace, sits down at their table to explain the legend that there is an enormous dragon living in the ice passages under Iceworld. Mel realizes that the Doctor must have come to search for the dragon. Ace, tired of working as a waitress, asks if she can come along. The Doctor agrees, and Ace asks if they are going to look for the treasure the dragon is supposed to be guarding. At the next table, Glitz overhears the conversation and tells the group that the treasure is just a legend, and not to waste time looking for it. Ace asks why he's spent days studying his treasure map if he doesn't believe in it. She walks over and pulls the map out of his hands.
Belazs reports to Kane, who informs her that he rigged the game so that Glitz would lose his money. He reveals that he arranged for Glitz to acquire the map, so that he would have to seek the treasure to avoid losing his ship. Belazs tells Kane about the Doctor and Mel, and asks if he wants them eliminated. He says no, as there is no reason for them to know there is a tracking device in the map's seal.
The Doctor is fascinated by Glitz' map, but Mel and Ace are both suspicious of anything that comes from Glitz. Glitz insists that he got the map from an unimpeachable source, but finally admits that he won it in a card game. The map is of the lower levels of Iceworld, where no one ever goes. The Doctor is intrigued by mentions of an ice garden and singing trees. Glitz tries to discourage the Doctor by pointing out other features, like the lake of oblivion or the depths of eternal darkness, but he only serves to excite the Doctor's enthusiasm further. The Doctor folds up the map, and he, Mel and Ace prepare to leave together in search of the dragon. Glitz leaps up, snatching back his map, and insists that they can't go without him. Furthermore, he refuses to take Mel and Ace along, claiming that it is too dangerous for women. Ace yells at Glitz for his chauvinism and storms off in a fury. The Doctor tries to back out, but Mel insists that he go along without her. She sits back down at the table as Glitz and the Doctor leave the restaurant.
Belazs reports their departure to Kane, noting that only two of the party left. Kane instructs her to continue monitoring the tracking device. He turns away, but then realizes that Belazs is still watching him. Impatiently, he asks her if there is anything else. She asks, since the Doctor and Glitz are as good as dead, if she could have the Nosferatu. Kane coldly reminds her that when she came to him, she had nothing, and was glad enough to accept his pay then. He removes a glove and menaces her with his bare hand and threatens to place her in cryogenic suspension, where she will lose all of her memories. He grabs her wrist, revealing a circular design burned into her palm. He says that as long as she has his mark, he owns her, body and soul. He raises a guard on an intercom, and orders the Nosferatu destroyed.
Back in the restaurant, Mel is blaming Ace for encouraging The Doctor and Glitz. One of the customers calls Ace over and rudely insists that her milkshake is unsatisfactory, and orders her to fix it. Ace loses her temper, yelling at the woman and dumping the milkshake over her head. The manager fires her, and when Ace tries to apologize, he kicks both her and Mel out. As he goes to placate the customer, Ace dumps a milkshake over his head as well before she walks out.
In the depths of Iceworld, Kane lies in a cryogenic cabinet different from those used on his mercenaries. A computerized voice announces the temperature in the chamber is dropping towards a goal of -193 degrees Celsius.
Ace and Mel enter Ace's room. Ace complains about Glitz, while Mel argues that he's all right underneath. When Mel criticizes the mess in Ace's room, the younger girl tells her she sounds like her teachers from school. Mel realizes that Ace is from Earth. Ace says she is from Perivale, but she didn't like it there. Ace liked chemistry, and was doing as experiment to extract nitroglycerin from gelignite. Something went wrong, and a time storm came out of nowhere, and carried her to Iceworld. When Ace says she doesn't want to ever go back, Mel asks about her parents. Ace goes into a fury, shouting that she never had parents, and doesn't ever want to have them. Mel attempts to calm Ace by changing the subject and asking about her chemistry A-levels. Ace says that she was expelled after blowing up the art room as a creative statement.
An intercom voice asks any emergency staff to report to the docking bay. Ace, tired of nothing being done about the ice jam, pulls out several old deodorant cans and hands them to Mel. Ace tells her they contain nitro-9, a compound of her own creation that is just like regular nitroglycerin, but with more wallop. Warning Mel not to drop the cans, Ace leads her out of the room.
Belazs looks in as Kane's cabinet continues to drop in temperature. Certain that he cannot observe her, she contacts the man who was ordered to destroy the Nosferatu and tells him that Kane has changed his mind, and not to destroy the ship.
The Doctor and Glitz are down in the ice passages. Glitz says that they are still too close to the surface to see any of the more interesting things on the map. Glitz tries ineffectually to guide them, but the Doctor takes over and chooses passages seemingly at random and pulling Glitz in his wake.
Several guards are attempting to remove the ice jam. They are trying to simply push against it and move it. Ace and Mel arrive, and Ace interrupts the guards, attaching two cans of nitro-9 to the ice block, then tells the guards they have eight seconds to get away. The guards dive for cover, and the nitro-9 explodes, completely destroying the ice block. Ace and Mel shout in excitement.
Belazs enters Kane's chamber. She examines the instruments, then turns to study the ice sculpture the artist was carving earlier. Kane's chamber reaches its optimum temperature and opens, and Kane steps out behind Belazs, demanding to know why she is in the restricted zone. She claims that she was looking for him to tell him about the ice jam. Kane becomes angry at being bothered with minor details, and tells Belazs to go to the docking bay and take care of the problem herself. She leaves.
The Doctor and Glitz enter a brightly-lit room full of large crystals. The Doctor deduces that these are the singing trees, based on their vaguely tree-like shape. The tinkling, singing sound is made by air vibrating the crystal membranes on some hanging, leaflike growths. Glitz picks up a crystal shard, and the Doctor discovers that it is some form of optical electronic circuit. When Glitz realizes that the crystal room is artificially constructed, he is afraid the dragon made it. He tries to leave, but the Doctor pulls him on.
Ace, Mel and the guards are examining the entranceway, no longer blocked by ice. Belazs appears with another set of guards. She demands to know what is going on, then places Ace and Mel under arrest. The guards grab the pair over their protests, and carry them off while Belazs follows.
The Doctor and Glitz are walking down another corridor. Looking closely at the map, Glitz takes a side turn, gesturing at the Doctor to follow him. Unfortunately, the Doctor is absorbing with looking at something else, and doesn't see. He discovers that Glitz is gone, and wanders off, calling for him.
Kane is interrogating Ace, while the guards hold Mel at a distance. When Kane discovers that he cannot intimidate Ace, he becomes intrigued by her, and offers her a position in his mercenary army. He describes the wonders of the twelve galaxies that he could open to her. When Mel tries to warn Ace not to listen, Kane asks Ace how old she is. She almost says 16, but corrects herself to "18." Kane continues to try to win Ace over by appealing to her wandering spirit. He asks her to take his gold sovereign, which he places on a console beside Ace. It is the imprint of this coin that was burned into Belazs' hand. When Mel tries to shout another warning, Kane orders her to be frozen. Ace hesitates, then knocks the coin to the ground, whipping out another can of nitro-9. She uses it to hold Kane at bay while ordering the guards to release Mel. Together, the two women escape and run down the corridor.
The Doctor emerges onto a parapet overlooking an enormous ice cavern. Hanging his umbrella from the rail, he begins to clamber over.
Ace assures Mel that she knows where they are going. Mel is just nervous because of the dragon. Ace assures Mel that there is no such thing, but while she says it, an enormous, looming shape towers behind her. Mel screams...
The Doctor is now hanging from the edge of the parapet. He is unable to get a firm grip, and grabs his umbrella in an attempt to flip around. He hands begin sliding down the umbrella, lowering him well past the lip of the ledge, dangling over the enormous chasm...
The Dragon fires blasts at Mel and Ace, and the two women jump out of the way. Realizing that the dragon is firing laser beams, rather than breathing fire, Ace deduces that it isn't a real dragon. When the dragon opens continues firing, the pair turn and run.
Glitz walks up to tell the Doctor that he's found the Ice Garden, with neither dragon nor treasure. When the Doctor points out that he's about to fall to his doom, Glitz nonchalantly agrees to help him.
In another part of Iceworld, Kane is criticizing Belazs for allowing Mel and Ace to escape. He tells her that they should have been searched for weapons the moment they were arrested. He warns her not to take advantage of his former feelings for her, because the past is an empty slate to him. He requires absolute obedience, and never forgives those who betray him. In order to stop Mel and Ace from uniting with the Doctor and Glitz, he releases Glitz' crew from their cryogenic stasis, ironically allowing them their revenge.
Glitz helps the Doctor reach the bottom of the chasm safely, nearly dropping him in the process. Once they are settled, Glitz despairs of getting the treasure before the 72-hour period is up. The Doctor suggests that Glitz explain the situation to Kane and work something out, but Glitz explains that Kane is completely heartless. As Belazs listens in through the device implanted in the map of Iceworld, Glitz explains to the Doctor that if Kane knew they were looking for the treasure, they would be killed. Instead, since he doesn't think he can get the money, Glitz has decided to hijack his ship, the Nosferatu, and he wants the Doctor's help. At first the Doctor has no interest in the plan, since he considers discovering a new species in the dragon to be more important. Glitz offers to give the map to the Doctor and Mel in exchange. The Doctor, knowing that he can't hope to find the Dragon without the map, finally gives in. Glitz happily turns over the map. Belazs switches off the listening device as her face creases in anger.
Kane watches the sculptor complete his work, which we learn is of Kane's former partner, Xana. He laments the waste of her criminal genius when she was killed while escaping arrest.
Mel and Ace reach the chasm. They spot the Doctor's umbrella, still hanging on the rail. Mel wonders how they will follow, and Ace supplies a portable ladder from her bag. The pair hangs the ladder over the side of the chasm, and contemplates the drop.
The Doctor and Glitz arrive at the Nosferatu. Seeing there is only one guard, Glitz tells the Doctor to distract him while he sneaks about the ship. The Doctor strolls up and attempts to engage the guard in a discussion about the nature of existence. The guard proves surprisingly interested in the topic, and Glitz slips by completely unnoticed. His task done, the Doctor attempts to retreat, but the guard backs him against the wall, eager to continue the conversation.
Mel and Ace begin the precarious climb down, and Mel grabs the Doctor's umbrella en route.
Glitz enters the Nosferatu, and immediately straps himself into the pilot's seat. Before he can take off, however, Belazs steps out of the shadows and places a gun at his temple, ordering him not to touch the controls.
Mel and Ace reach the bottom of the chasm, and head off to find the Doctor.
Belazs declares that the ship is hers. When Glitz complains that his 72 hours aren't up yet, Belazs says that she will have to ensure that he doesn't get the money, and prepares to shoot him. The Doctor walks in at this moment, and Belazs turns to train her gun on him. She declares that only one person can leave on the Nosferatu, and it will be her. When Glitz asks what Kane thinks of her plan, she exclaims that Kane doesn't own her. The Doctor, sensing an opening, says that he thinks he does. He suggests that she sold herself to Kane long ago, asking her if it was worth it. Belazs lifts her hand in rage, showing the Doctor the mark on her palm, saying that is what she sold herself for. While she rants, Glitz spins behind her, wrenching away the gun and turning it on Belazs, who boldly challenges Glitz to kill her. Glitz says they should just put her off and take the ship and run. The Doctor convinces Glitz that he can't keep stealing everything, and to face up to the situation. He sadly looks at Belazs' hand, saying that he doesn't think she can ever pay of her debt.
Kane and the sculptor look at the now-completed ice sculpture of Xana. Kane commends him on his excellent work, but then explains that no one can ever see the results of his work. As the oblivious sculptor studies his achievement, Kane removes his gloves and steps up behind the sculptor, telling the man to die fulfilled as he applies his icy grip to the sides of his head, and the sculptor begins to collapse.
Mel and Ace cautiously turn corners as they search for the Doctor and Glitz. Ace pauses when she hears something. They see members of Glitz' crew approaching them, zombie-like. They turn around, to discover that other members have sneaked up behind them, and one man is training a gun on them. They scream, and race off down a side corridor.
The Doctor and Glitz, now back in the bowels of Iceworld, are looking for the Dragon once again. The open a hatch and pass through. The Doctor consults his map, but then both men hear growling ahead. They slowly inch ahead to the corner, and peer around. The dragon, standing waiting, fires lasers at them. The men cry out and race back, slamming the hatch closed behind them. They pause to rest. When sparks begin shooting through the door, the Doctor realizes that the dragon is using its lasers to cut through the hatch. They pair back away from the door.
Mel and Ace are still running from the crew. They duck into a crevice, and Mel tells Ace to cover her ears as she pulls cans of nitro-9 out of Ace's bags. After she hurls two cans at their pursuers, knocking them flat, Mel and Ace begin to congratulate themselves. Their celebration is cut short, however, when one of the men begins to stand. Ace can't believe anyone could survive her explosives, but the girls begin running as the crewman begins to pursue them once again. They run around a corner, and Mel falls and knocks herself out on the edge of a step. Ace pulls her around and under the stairs, as the crewman walks up. He walks up the steps and pauses to look around, then lumbers off. As Mel regains consciousness, Ace assures her that the pursuit is gone.
The dragon has finally cut through the hatch, as the Doctor and Glitz look on. As the dragon passes through the opening, Glitz raises his gun to fire. The Doctor grabs Glitz' arm and wrestles the gun from him. He throws it away as he explains that they have no right to kill. The dragon observes the exchange, then turns and walks away. Glitz wants to know why the dragon didn't kill them, and the Doctor suggests that they ask it.
Kracauer finds Belazs in the control room. She begins to complain about the years she's spent in Kane's service. She laments that she was only 16 when she accepted his sovereign. They compare their marks, and she cries that it should start to disappear after twenty years. Kracauer points out to her that they had a choice, and Belazs argues that Kane will find younger replacements and kill them unless they kill him first. Kracauer asks if she has a plan, and she explains that she has seen the restricted zone, and she knows that even Iceworld is to hot for Kane, and that he uses refrigeration units to lower his body temperature whenever it rises too high.
Mel and Ace are still resting on the stairs, and Ace pulls a thermos of coffee out of her bag. As she pours for them, she tells Mel that after she was kicked out of school, she began to work as a waitress, and that her entire life was boring and tedious. She always felt that her life was wrong, and that she was supposed to be somewhere else. She fantasized about being able to escape into the stars, to her real family. Then she actually managed to escape and come to Iceworld. But here she just wound up working as a waitress again, and now she couldn't even dream of escape, because she'd already gotten to the stars.
Kane looks on the statue of Xana. He promises that when he returns home, he will erect statues in her honor. Then, he enters his refrigeration unit and the computer records the dropping temperature.
As she finishes the coffee, Ace turns serious and swears Mel to secrecy, then tells her that her real name is "Dorothy." She complains about what a terrible name it is, then the two women exchange a smile and return to their journey.
Kracauer enters the restricted zone. He assures himself that Kane is secure in the refrigeration unit and oblivious, then he walks to the control panel and changes several switches. He turns back to watch Kane as the computer records the rising temperature in the cabinet.
The Doctor and Glitz are finally reunited with Mel and Ace. Ace and Glitz begin to argue, but the Doctor interrupts them. The Doctor tells them that the dragon is not really a dragon, but a semi-organic vertebrate. The women tell the Doctor about their encounter with the dragon. The quartet set out in search of the dragon once more, but is cut off by the crewman, who has caught up with them at last. Ace tells the Doctor about Kane's cryogenic army, when Glitz recognizes the man from his crew as Pudovkin. He attempts to talk to Pudovkin as old friends, while the Doctor explains that it is impossible for Pudovkin to remember anything after being cryogenically frozen. When Pudovkin does remember Glitz, the Doctor realizes that the only exception is in cases of overwhelming hatred and anger. Pudovkin advances, saying that he remembers Glitz taking the best of everything in their hauls, and then selling them into slavery. He raises his gun and is about to fire when the dragon, which has crept up behind the Doctor and his friends, blasts him with its lasers. The Doctor doffs his hat to the approaching creature, which returns the gesture. When the Doctor tries to talk to it, the dragon waves for the group to follow and walks off. The Doctor and his friends trail behind.
In the restricted zone, water begins to pour down the statue of Xana as the temperature rises above freezing. The refrigeration unit opens and Kane stumbles out, gasping for breath. When he sees Kracauer, the Sergeant backs away in fear. When Kane sees the ruins of the statue, he lashes out in fury, killing Kracauer with his still-freezing grip. Kane pauses and whispers "Belazs." He replaces the switches on the control panel, and slumps against the computers in relief as cold air pumps into the room once more.
The dragon leads the Doctor and his companions into the room of the singing trees. While Mel and Ace look around in wonder, the Doctor notices that the dragon is interfacing with a computer. The Doctor realizes that the room is designed to produce holographic images, and that the dragon is using itself as a power source. The image of a woman dressed in white robes appears. It is a recording of a criminal case history for the leaders of the notorious Kane-Xana gang. Because of his evil nature, Kane has been permanently exiled from his homeworld of Proammon. They selected Svartos for his exile because its permanently frozen dark side would permit him to survive.
Belazs is standing in the control room when Kane walks in. He pleasantly tells Belazs that he has reconsidered her request to leave, and that she is free to go. Her eyes open in wonder as he bids her happiness, then he lashes out, grasping her face in his hands, spitting invective about his three thousand year imprisonment as she struggles and fades.
The woman in the image explains to the group that Kane's partner, Xana, killed herself during the final siege of their headquarters to avoid arrest. The image fades. Mel wants to know where the dragon enters the picture, but Glitz just wants to know where the treasure is. The Doctor deduces that, since Kane is extremely vulnerable to heat, the "fire-breathing dragon" was left to guard the treasure. In fact, he speculates, perhaps the dragon itself is the treasure. At this, the dragon's head opens, exposing a mass of circuitry and wiring, and a crystal, coursing with electricity, emerges from the depths of the dragon's brain. Glitz wonders what it is worth, but the Doctor points out that its real value is as an immense source of optical energy.
Kane is listening in through the device in the map, and he declares that after three thousand years, the dragonfire will be his.
Kane contacts his new head of security, and informs them that there is an aggressive non-terrestrial in the lower levels, marked with a radio-tracking device. He orders them to kill the creature and bring him its head.
Glitz continues to covet the treasure, and Ace comes to the dragon's defense. While they argue, the dragon's head closes and conceals both the gem and the inner circuitry. The Doctor muses over where he has heard of the planet Proammon before. The Doctor wants to go back to the TARDIS and consult his star charts. Ace is excited at the prospect, but Mel points out that there isn't time. Glitz reminds the Doctor about the Ice Garden, and the Doctor realizes that the garden is a primitive star chart. The Doctor and the dragon stride off, leaving Glitz alone with the hostile women.
Bazin is selecting his weapon for the ANT (Aggressive Non-Terrestrial) hunt. When McLuhan, a more experienced guard, sees his selection, she points out that he has never been on an ANT hunt before, and frightens him with stories of two-meter tall scorpions. Then she takes his gun from him and pulls out heavy artillery, throwing it across the room to him. They leave to begin their hunt, with the now extremely nervous Bazin trailing behind McLuhan.
Mel suggests to an incredulous Ace that they play games to pass the time.
The Doctor has once again become lost in the Ice tunnels. The Dragon indicates for him to follow, and he allows the creature to take the lead.
Kane has summoned his cryogenic army. He orders them to create panic throughout the upper levels, driving everyone towards the Nosferatu and leaving Iceworld completely uninhabited. The army shambles off to carry out the orders.
McLuhan gives the radio receiver to Bazin, who attaches it to his weapon. She instructs him to watch for the ANT's movements.
The Doctor and the dragon have reached the Ice Garden. He examines the star chart, but the stars are all out of place, and the chart is of no use. The Doctor realizes that Kane and the dragon must have been on Iceworld for thousands of years to allow that much star drift.
Ace is becoming increasingly bored. She realizes that she has run out of nitro-9, and she and Mel both perk up at the excuse to return to her quarters and get more. Glitz squashes their excitement when he points out that there is more stable commercial explosive on the Nosferatu. After a brief argument, Glitz leaves the two women alone while he goes to fetch explosives. The now depressed Ace begins a half-hearted game of "I Spy" with Mel.
Back in the restaurant, a young girl named Stella crawls under the table to play with her bear. The soldiers burst in, scattering everyone in terror. Stella, unnoticed beneath the table, is left alone. When she emerges, she helps herself to a milkshake, then wanders off.
The Dragon begins to lead the Doctor away when Bazin and McLuhan catch up. The Doctor is separated during the firefight, and the two guards leave in pursuit of the dragon without noticing him. They later begin to panic when the radio receiver picks up the signal right on top of them. Bazin fires in a panic, narrowly missing what turns out to be Stella. While they are preoccupied with her, the dragon comes up behind them and fires on Bazin. McLuhan leads the wounded man down a side tunnel while the dragon examines Stella.
The Doctor returns to Mel and Ace. When they tell him Glitz went back to the Nosferatu, the Doctor says they have to follow him while there is still time to stop Kane and save the dragon.
The Doctor explains to Mel that the only way to save the dragon is to convince Kane that the star charts are hopelessly out of date and useless. Ace only cares that she is about to actually get to see the inside of the Doctor's spacecraft.
The Dragon returns Stella to the upper levels, which are now deserted. She happily wanders through the empty corridors, obliviously playing with her doll.
Glitz arrives back at his ship, just in time to see it undock, filled with all of the frightened visitors to Iceworld. Glitz watches his ship take off in despair.
Kane pushes a button on his console, and the Nosferatu explodes in space. Glitz watches from a bay window in horror. His face sets in anger, and he is determined to get revenge on Kane.
The Doctor, Mel and Ace reach the TARDIS. Mel talks to Ace while she reacts incredulously to the ship, but the Doctor is preoccupied. Consulting his charts, he discovers that there is no planet Proammon. The Doctor shouts for them to be quiet, then leads them back out of the TARDIS without explaining what he has learned. Ace splits from the other two to go back and get more nitro-9. The Doctor grumpily pulls Mel away and back onto their mission.
Glitz encounters Stella's mother, who is oblivious to the terror that has overtaken the station. She casually asks if Glitz has seen her daughter, then wanders off.
Ace enters her room and walks towards her bed, then stops and turns as she senses a presence. Kane is standing directly behind her.
Bazin and McLuhan lie in wait and ambush the dragon, which they kill. Despite Bazin's squeamishness, McLuhan cuts off the creature's head. As they pull it away, it opens and reveals the crystal within. Lightning from the crystal kills them both.
Glitz comes into Ace's room. He picks up an icicle that he finds attached to the door of the room, but it is so cold it burns him. He drops it and moves on. Ace's room is empty, and there is no sign of her, or of Kane.
Mel and the Doctor find the bodies of the dragon and the guards. The Doctor removes the crystal from the dragon's head and hands it to Mel, determined to put an end to the death and destruction.
The Doctor and Mel run into Glitz. When he realizes that Ace is missing, the three set off in search of her. Shortly after, Kane uses the intercom to announce that he has Ace, and is willing to trade her for the dragonfire. If the Doctor doesn't agree quickly, Ace will die. Mel argues that the Doctor can't give the dragonfire to Kane, but the Doctor says that since the dragon is already dead and Ace is alive, he has no choice. He leads the two off.
Stella finds Kane's inner chamber, and sets her bear doll in his cryogenic freezer for a nap.
The Doctor and his companions arrive at Kane's command center for a confrontation. The Doctor knows that Kane is three thousand years old, and wants to know why someone who has waited so long is in such a hurry. Kane realizes that the dragon led them to the archives, and says he should have destroyed them. The Doctor cryptically says that he should keep them as souvenirs, along with the Ice Garden. Kane explains that the dragon was his jailer, keeping watch over Kane in his imprisonment. The dragonfire is the energy source necessary to fully power the complex's controls and allow him to escape.
Kane demands that Mel give him the dragonfire, but she refuses. Ace begs for her life and Glitz urges Mel to turn over the crystal. When the Doctor tries to explain something to Kane, he spins Ace around and menaces her with his freezing hands. The Doctor acquiesces, and Mel places the dragonfire in the central console. The complex begins to shake, and the central section breaks free and takes off; it is a spacecraft.
Kane declares that his vengeance is at hand. He will gather new mercenaries and retake his home planet. The Doctor tells him to examine his controls now that they are fully functional. Kane realizes that something is wrong; the controls tell him there is no planet at all. The Doctor tells him that Proammon's star went supernova one thousand years after Kane's imprisonment, and the planet no longer exists. Kane refuses to accept life without his planet. He opens a window on a chamber that radiates unfiltered sunlight. The scorching rays reduce his body to nothing.
Glitz has taken over the ship and renamed it the Nosferatu II. The Doctor is in the TARDIS preparing to leave when Mel tells him that she thinks it is time she left. She is surprised by the Doctor's intense reaction, first grumpily refusing to talk to her, then growing melancholy and depressed. Glitz arrives to bid them farewell before he takes Ace home to Perivale. Mel asks if he can take her as well. He agrees until he realizes that she means to stay on the ship, and keep him out of more dodgy deals. The Doctor and Mel fast-talk him into agreeing. As they walk out of the TARDIS, Mel whispers to the Doctor that Ace has nowhere to go. As Ace prepares to follow the others out, the Doctor pulls her aside. He asks her if she would rather take the scenic route home with him. She enthusiastically agrees.
Stella approaches the outside of the TARDIS when her mother finally finds her. Still oblivious to everything that has happened, she berates her daughter for wandering off and tells her to follow. Stella pauses and watches as the TARDIS disappears, then smiles.
Source: Dave Doty
Mel returns in Head Games
, when she is captured by the Doctor's fictional counterpart Dr. Who.
Ace arrived on Iceworld thanks to a time storm caused by a chemistry experiment. How that happened is revealed in The Curse of Fenric