The Doctor is taken to Bowie Base One where Adelaide and many more of her crew are there to witness his arrival. Immediately he is held under suspicion - and not a little awe - at being an unexpected new arrival on an unpopulated planet. He manages to gain Adelaide's trust enough for her to lower her gun but she insists that the robot - named GADGET - keeps him under surveillance. In actual fact GADGET is being controlled by another of the crew, Roman Groom, who activates the machine with an arm-mounted control panel.
Soon Maggie Cain, another crewmember working in the base's bio-dome, contacts Adelaide to ask about the Doctor's arrival. She is dismissed for her casual manner and receives no answers. She complains to her co-worker Andy Stone, but he is more interested in the carrots he has successfully managed to cultivate on the surface of the planet. Washing them under a tap he rejoices at this accomplishment and takes a bite from one of them.
Maggie continues to ponder the intruder upstairs and which government on Earth might have been behind the infiltration. She does not notice Andy dropping to his knees behind her and convulsing wildly. When she does see him she begins to grow worried - he does not speak, only the sound of running water can be heard. She approaches him and he turns to face her. His eyes have changed to an eerie white colour, the skin around his lips is badly blistered and his mouth is blackened. Water gushes from his jaws and he growls. Maggie screams.
Back in the control room the Doctor bluffs his way through interrogation to learn the names of his captors. When Adelaide mentions that they are the very first off-world colonists he recognises them, their names: Captain Adelaide Brooke, Deputy Ed Gold, Tarak Itel MD, Nurse Uri Kerenski, Senior Technician Steffi Ehrlich, Junior Technician Roman Groom and Geologist Mia Bennett. With each of the names he sees flashes of their profiles printed on websites, and upon learning the date - November 21, 2059, he recalls another - the destruction of the base upon this very day. With each of the names he recalls is the date of their death.November 21, 2059.
Suddenly he declares that he must leave and heads for the exit, claiming that he has no choice but to go and not interfere with what is happening on Mars. He bids farewell to the crew one by one, even GADGET, and then Adelaide, before recalling the other two members of the crew - Margaret Cain and Andrew Stone (also both noted in history as having died on this day). Ed opens a communication line to Maggie to offer her the chance to meet the Doctor, but all that is heard in reply is a deathly growling.
The Doctor reiterates that he should leave but when Adelaide and Ed discover the security cameras in the bio-dome are down and that the power is being cut inside, he is ordered to help them investigate since the problem has occurred shortly after his arrival.
Adelaide takes the Doctor, Tarak and GADGET (guided by Roman back in the control room) on foot to the bio-dome. The Doctor asks the stern captain the one question the history books cannot answers - how she felt to be the leader of the first expedition to Mars. She recalls the chaos of climate change back on Earth and how she was able to leave that and stand on an untouched world. Smiling for once, she tells him her devotion to the trip has been worth any cost.
Suddenly they see a body in the long tunnel leading to the dome. It is Maggie - still breathing but unconscious. Tarak calls Uri to bring a medical kit and he hurries to meet them. Ed also runs to join the party, despite procedure dictating otherwise. When they arrive in the tunnel Adelaide immediately orders him back. Tarak tells Uri to isolate Maggie in quarantine and then prepares to proceed to the bio-dome with the Doctor and Adelaide whilst GADGET stands guard.
Back in the main dome, Steffi and Mia analyse the growling heard on the intercom, which is identified by the computer as Andy's voice. Steffi alerts Adelaide who tells her to double check. She, Tarak and the Doctor arrive in the bio-dome and search for Andy. The Doctor manages to restore the lights with his Sonic Screwdriver and then goes to investigate the dome with Adelaide whilst Tarak checks the doors are secured.
Uri calls from the medical bay to alert them that Maggie has awoken, but is unaware of what has happened to herself or Andy. Ed tries to ask question her further over the communication channel but Adelaide orders him to be silent. Maggie asks to be let out of isolation but Uri tells her she must stay there for twenty-four hours.
In the bio-dome Tarak continues the search for Andy. He sees him standing some distance away, his clothes and hair saturated with water, which pours out of his fingers. His back is turned. Tarak approaches him but as he does Andy turns and hisses through his possessed mouth.
Back in the medical bay Uri watches a recording of a video message sent by his brother and laughs, recalling the outrageous spending of his brother-in-law back on Earth. He is unaware that in the isolation chamber behind him, Maggie has started to convulse. When the tremors end she asks him, in her normal voice, about the Earth. She comments on how much water it has.
"We should like that world".
Her voices changes to an eerie, deep tone and Uri turns to face her. Like Andy, her mouth has become blistered and she exhales water, a menacing smile on her face. Uri contacts Adelaide to warn her, and she tells him to remain calm. He relates her symptoms and immediately Adelaide realises that the bio-dome is no longer safe.
She calls to Tarak to form a retreat but there is no reply. She runs to find him, the Doctor following close behind. Eventually they find him, knelt on the floor before Andy, who places a hand on his head, causing him to convulse as water pours over him. When Adelaide raises her gun Andy stops, but it is too late - Tarak has already been possessed.
The Doctor and Adelaide flee, followed closely by Andy and Tarak. They narrowly make it out of the bio-dome - sealing the doors as they go - before Andy unleashes a jet of water from his hand. They watch the two possessed humans through the locked door, Andy looking carefully at the barricade.
Ed arrives in the medical bay in time to see Maggie displaying similar symptoms - Water oozes from her palms as she presses them up against the quarantine glass. He contacts Adelaide to confirm that Maggie is contained and in return the captain orders her crew:
"Don't drink the water. Don't even touch it. Not one drop."
Meanwhile, the Doctor gazes at Andy through the bulkhead glass, but insists once again that he cannot probe into the matters unfolding on Mars. When Andy and Tarak begin bombarding the door with water - thereby fusing the lock systems - he and Adelaide retreat.
Soon Andy and Tarak are after them again but the Doctor has a plan - returning to the tunnel he uses his Sonic Screwdriver to reprogram GADGET and enable him to move at massive speed. At last able to make a palpable escape he and Adelaide drive back to the main dome, once again sealing the doors to block out their pursuers. Adelaide protests her faith in the security system but the Doctor simply warns that the Water will not be defeated - it can erode entire planets if it waits long enough.
"Water always wins."
He and Adelaide then trek to the medi-dome to join Uri and Ed. The Doctor notices that Maggie's eyes are still human - unlike the washed-out irises of Andy and Tarak. Adelaide explains that all of the water used by the crew comes from a glacier underneath the base, but it is filtered before use. However, the Doctor knows something must be wrong for the infection to spread. Ed surmises that the glacier must contain some viral life-form, which has found its way into the infected humans by transition of water.
Ed takes Adelaide to one side and reminds her that now the safety of the crew is jeopardised she must initiate Action One - evacuation of the base. This she does and orders Mia, Steffi and Roman to prepare the rocket for emergency take-off. Roman is reluctant to leave GADGET behind but Steffi insists there is no room for him on the shuttle, he must be left in storage. They begin loading provisions for the journey. She, Ed and Uri then follow suit but the Doctor reminds them that if the infection was able to delay manifesting in Maggie in order to gain access to the bio-dome, then any other member of the crew might already be infected - the virus, like the water, can wait; manifesting only when it reaches Earth.
Adelaide goes to inspect the ice field and the Doctor, despite knowing morally that he should not interfere any further, goes with her. Uri, meanwhile, collects what he needs from the medi-dome and evacuates, leaving Maggie behind. Pressing her palms to the quarantine bay door she short circuits the locks and steps outside. Ed and Roman watch from the main dome, unsure of whether the other doors will hold her. At the moment the security cameras fail - they no longer know where Maggie is.
Still inside the medi-dome Maggie stands with her arms outstretched. Looking to the heavens she begins to scream. Across the base in one of the tunnels, Andy and Tarak hear her and, slowly and patiently, turn around and walk away.
Adelaide and the Doctor arrive at the glacier to begin examining the filtration system. The Doctor recalls the legends of the Ice Warriors, inhabitants of mars long since gone who built their empire in the snow - perhaps it was they who discovered the infection and sought to freeze it to prevent it from spreading.
Adelaide questions why the Doctor seems intent of leaving the base, and asks why he seems to know so much about the Bowie Base crew. He responds by claiming that his reluctance to involve himself in their troubles is because, deep down, he understands that this day and what happens to Adelaide and her crew is a fixed point, it must not be changed.
He turns the conversation back to Adelaide, recalling a story he knows her granddaughter will tell in the future - the story of the day Adelaide Brooke met the Daleks. She admits the tale is true. When she was a child the fearsome cyborgs stole the planet Earth and invaded its continents. Her mother was lost outside and her father abandoned her in an attempt to find his wife - neither was seen again. Left alone in her house Adelaide was seen by a Dalek as it surveyed the skies, but it did not attack her. Looking at her it simply turned away.
He tells Adelaide that seeing the Dalek was the beginning of a legacy - a destiny to lead mankind to the stars. He talks of her granddaughter Susie and how she will lead the first light speed mission away from Earth. Her descendants continue this exploration, carrying with them the name of Brooke. Adelaide asks who the Doctor is to know such things, and why he would tell her. To the second question he has only one answer - it is consolation for what is to come.
Returning to the computer they discover that Andy left a recording on the colony log the previous day. Upon examining it they discover that there was indeed a malfunction with the filtration system - one of the filter heads has broken and the replacements do not fit. The Doctor muses that one single filter has allowed the virus - the Flood - to break free, but Adelaide seems heartened by the news. Knowing that the infection has only just arrived, and that the water is filtered through the bio-dome once a week, she can be sure none of the rest of her crew is infected, and they can abandon base.
As Ed and the rest of the crew continue to stock their shuttle with supplies, Adelaide and the Doctor return to the main dome. Adelaide hands the Doctor his spacesuit and bids him leave. He watches as she returns to her crew to help them prepare, but trouble is already on its way. Up above, on the roof of the dome, Andy and Tarak have positioned themselves, flooding the surface with water. Soon Adelaide and Ed realise what is happening but refuse to acknowledge that the water might get through the hull. Adelaide orders Ed to the shuttle to prepare for take-off, and the rest of the crew resume their work.
The Doctor watches. He knows that this is the day Bowie Base One is destroyed, that all of the preparations made by the frantic crew will come to nothing. But he cannot interfere; the laws of his people will not allow him to change a fixed point in time. Turning slowly, he heads for the exit.
Donning his space suit he enters the decompression chamber, but something is blocking him access to the Mars terrain. Over the video link Adelaide tells him that she will not let him go before he tells her what it is he cannot prevent, what the fixed moment in time is. He feigns ignorance but she knows better. He tells her that there are events in history that are unavoidable, like Pompeii, and anything that he does to alter them will never truly avert the outcome, only alter it.
He tells her that although the crew is currently carrying out Action One - evacuation, history dictates that events will escalate so that Adelaide's only option is to execute Action Five - detonation of a nuclear device held at the centre of the colony so that nothing can survive, thereby denying the Flood access to Earth. He claims that it is this self-sacrifice that inspires her granddaughter to take mankind out into the galaxy, all because her grandmother dies on November 21, 2059.
Adelaide protests, determined that she will not perish, but the Doctor is adamant about her destiny. He knows that her passing is a significant factor in shaping the future and for that reason he cannot save her. He recalls the Dalek that saw Adelaide and spared her, theorising that it too knew that she must be preserved so that she could live out her place in history, fixed in time forever. Adelaide asks why he himself will not die on Mars with her and he tells her it is because she lets him go. With history against her she relents, cursing the Doctor but allowing him to leave.
At that moment the water breaks through the bulkhead, pouring into the control room. Adelaide orders her frantic crew to depart for the shuttle. Uri lead the way but finds the corridor blocked by a cascade of water. Steffi panics, fearing he may have touched the liquid but he is clean. Forced to change their root Adelaide directs the other once again.
All the while the Doctor is listening over the intercom in the decompression chamber, listening to the terrified cries of the Bowie Base colony.
In the control area Steffi hurries across the room to pick up more supplies but before she can return to the others the ceiling gives way and a torrent of water cuts her off, slowly advancing towards her. She is forced back into a tiny communication chamber, but even there she is not safe. The water begins to seep through the ceiling. Adelaide orders the others away and promises Steffi they will save her, but it is too late. Knowing her time is up, Steffi calls up a video on the computer screen - a message from her children back on Earth. It plays as she weeps, the water spilling over her.
And all the while the Doctor is listening. Departing the airlock and walking out onto Mars' surface he can hear in his head the cries of the doomed.
Adelaide and Mia watch as Steffi's body convulses, the Flood taking control over her. Possessed, she steps out of the communication chamber and walks slowly towards Adelaide, who retreats with the others en route to the rocket, which Ed is preparing for take-off. The engines roar to life.
And all the while the Doctor is listening, walking away as commanded by time.
Adelaide, Mia, Uri and Roman slowly make their way toward the shuttle, forced to channel their air supply through each section of corridor before they can proceed. In a passing glance Roman looks up at the ceiling. A water droplet has formed on the surface and falls silently onto his cheek. Adelaide can only watch as he apologises for his folly, and his body begins to shake.
nd all the while the Doctor is listening.
In the shuttle Ed is still making preparations, seated in the pilot's chair. Suddenly he sees Maggie approaching up one of the service ladders. He tries to seal the door but she manages to fire a jet of water at him. Breathing heavily, fighting the infection, he contacts Adelaide and tells her the shuttle is down. He knows the Flood needs the shuttle to get to Earth and that leaves him only one option. With his final breaths he curses his job and Adelaide for never giving him the chance to shine. She never forgave him. He activates the self-destruct circuit and the craft is blown to smithereens.
And all the while the Doctor is listening. He is thrown to the floor by the force of the explosion. Another life lost.
The blast bounces back and hits the rest of the base, fracturing the hull. Adelaide, Uri and Mia are left surrounded by debris, flames and rushing wind as the oxygen begins to desert them.
And all the while the Doctor is listening; he can see them in the burning ruins of the colony. But there is something else inside his head; another voice - his own - recalling, so many times, the loss of his people. How he is the last of his race, how the old order was destroyed in a fury of flame and how he was left alone.
The last of the Time Lords.
He returns to the base and calmly walks through the chaos. He grabs a canister of sealant and tells Mia to fix the hull, then orders Uri to open an emergency bottle of oxygen from his medi-dome supplies. Helping Adelaide to his feet he swaggers across the room. She warns him that their fates are sealed and tells him not to allow himself to die with them. However, the Doctor claims fate is not his concern - he was told himself of destiny, that "he" will knock four times and end his life, and although he claims to understand what this means, he knows it is not going to happen on Mars.
At that moment Andy reaches the door and begins to knock. After three the Doctor leaps into action, sending a surge of power through the bulkhead and electrocuting him. He then turns his attention to the rest of the Flood, realising that they need heat to defeat the infection, by raising the temperature they can reduce the water to vapour. Adelaide again protests, recalling the Doctor's earlier claims that she and her crew all die on Mars. However, the Doctor now tells her that although there are rules governing time and those who traverse it, the people who guarded them are dead.
"D'you know who that leaves? Me! It's taken me all these years to realise; the laws of time are mine, and they will obey me!"
Suddenly one of the computers explodes, denying him access to the temperature controls. Adelaide tells him history has other ideas. He then decides tat they must escape the base and go outside - but the spare spacesuits are in another room which is sealed off by the water. The Doctor, now breathless and manic, tells his three companions that they are not simply fighting the Flood, they are fighting time itself, and he intends to win.
Down in the glacier, Maggie arrives and begins a summons. As she emits a deathly scream the ice begins to fracture - the Flood is on its way.
The Doctor furiously thrashes through his brain, trying to think of how to save the others. He asks what is left that they can access and utilise, but Uri claims it is only storage. However, this is all the Doctor needs. For locked away in storage is GADGET. He places something in the robots hand and then uses the remote control to direct it outside. Adelaide watches sullenly and then turns to the computer keyboard, preparing to launch Action Five. The Doctor sees and warns her that he is prepared to fight her as well in order to win his battle, but she activates the countdown regardless.
Meanwhile, GADGET has arrived on the planet surface and, thanks to the Doctor's modifications, is able to hurtle away across the planet's surface. With the Doctor at the controls the robot eventually arrives at the TARDIS and, having been given the ships' key, is able to open the door.
The Doctor cheers as the base begins to deteriorate around him, Uri and Mia still fighting to contain the collapse whilst Adelaide looks on, defeated. Across the colony the possessed Andy, Tarak, Steffi, Maggie and Roman all scream, welcoming the release of the Flood.
Under the Doctor's guidance GADGET activates the TARDIS controls and sets the ship in motion. As the final seconds of the countdown begin the sound of the ship materialising is heard, and the Doctor is ready.
The nuclear device detonates, reducing the colony to dust and wiping out the Flood. Just as history and time dictate, Bowie Base One has been destroyed.
But the Doctor has not been defeated.
The TARDIS arrives back on Earth, on a silent city street lined with houses, covered in snow under a starry night sky. The Doctor, Adelaide, Uri and Mia all step outside, accompanied by GADGET, who promptly shuts down now that his signal from Mars has been destroyed. Adelaide recognises her house a few feet away. The Doctor, wishing to be thanked, explains that he has brought them to Earth on November 21, 2059; it is the same day, and they are safe. Mia gazes at the TARDIS, astonished by what she has just seen inside. Overwhelmed she turns on the Doctor and then flees, with Uri following close behind on Adelaide's command.
Left alone, Adelaide confronts the Doctor, claiming that now he has saved her, her granddaughter will not become he woman she would have had her grandmother died saving the Earth. The Doctor insists that she still will, only now her inspiration can be gained directly - the same story but with one detail that he has changed. Adelaide is not convinced by this, claiming that if her family history changes then so too could all of Earth's. The Doctor claims that this is tough, for now he is in command of time, and he alone. He is not the lost soul of the Time War, he is the winner: The 'Time Lord Victorious'.
Adelaide is horrified by his sudden callous change of tone, and venomously calls this newfound title wrong. However, the Doctor simply claims that that decision is his to take. He turns to her house and opens the front door with his Sonic Screwdriver. She takes a few steps forward and then addresses him one last time.
"Is there nothing you can't do?"
She turns and walks toward her home, as he returns to his TARDIS. She walks over the threshold and, taking her gun from its holster hanging around her waist, she closes the door. As the Doctor reaches his ship a single shot is heard. He turns in horror. Suddenly time rewrites itself again and the history books are rewritten Adelaide Brooke still died on November 21 2059, but on Earth, not Mars. The same story but with one detail he has changed.
A look of horror crosses the Time Lord's face as he realises that Adelaide was right, the Time Lord Victorious is an abomination. Soon he hears singing, a sorrowful tune drifting on the air. He turns around to see Ood Sigma standing in the snow some distance away, calling to him, summoning him. Immediately he realises that he has gone too far in his actions and asks if this is the time of his death, as was prophesised. Ood Sigma gives no reply and disappears. Terrified, the Doctor quickly steps inside the TARDIS and disappears.
Stood alone in the console room, the cloister bell tolling, he solemnly realises that his life is drawing to a close. But the end is not yet upon him. Raging against the dying of the light, he leaps into action and activates the controls.