A vital clue to the nature of Sabbath’s mysterious allies may lie in a diamond locket which once belonged to a young Russian noblewoman. The Doctor traces the locket to the Kremlin Museum in the early 21st century, but when he, Fitz and Trix arrive they find two soldiers from the distant future looting the exhibits. When the Doctor intervenes, a fight breaks out and the room suddenly bursts into flame. Fitz and Trix overpower one of the soldiers, Kel Vorman, who is later revealed to be suffering from serious internal injuries caused by his journey through Time. The other soldier, Olrik Sund, uses a transit belt to return to his home time, and inadvertently transports the Doctor along with him.
Trix, Fitz and Vorman are removed from the flames by soldiers from the Russian division of UNIT (Operativnaya Gruppa Rasvedkoy Obyedinyonnih Natsiy, or OGRON). Colonel Grigoriy Bugayev is investigating a spate of art thefts, and he suspects that the corrupt businessman Vladimir Garudin, the head of the company Kronometr, is responsible. Fortunately for Fitz and Trix, Bugayev knows the Doctor of old, and decides that the Doctor’s companions may be able to help him. Also luckily for Trix, she was not searched thoroughly in the confusion, and Bugayev and his men don’t realise that she stole the locket from the museum.
The Doctor and Olrik Sund have been catapulted thousands of years into the future, along with a painting of a beautiful Russian noblewoman. Sund is obsessed with completing his mission and delivering the painting to the Lord General Razum Kinzhal, but this means crossing the winter wilderness outside Sverdlovsk on foot while trying to avoid enemy patrols. The Doctor decides to accompany him, intending to discuss the issue of historical piracy with Kinzhal himself. As they approach Sverdlovsk, the Doctor notes that, although he has survived relatively unharmed, this method of time travel causes serious damage to the human body -- yet Sund’s determination to deliver the painting is keeping him mobile long after he should be dead.
In this era, the Icelandic Alliance and the PacBloc are at war, and the brilliant strategist Razum Kinzhal has devised a complex plan to rout the PacBloc forces and destroy their leader, the evil Karsen Mogushestvo. The plan appears to go fatally wrong when Kinzhal and his young adjutant, Angel Malenkaya, are captured while scouting out Mogushestvo’s defences at Omsk -- but when Mogushestvo tries to “interrogate” Kinzhal by cutting into his brain with a neural scalpel, he triggers a hidden neural trap which stuns every living being in the vicinity except Kinzhal. Kinzhal and Angel flee from Omsk in a stolen Stepperider, but run over a field of heat-sensitive mines and must fire their plasma cannon to distract the mines by creating a new heat source. Mogushestvo detects the heat flare and, aching from his humiliation, sends his robot air force out to destroy Kinzhal; however, Kinzhal and Angel abandon the Stepperider at the last moment and watch from a safe distance as Mogushestvo’s air force is destroyed in turn by the Icelandic Alliance’s own robot drone planes. Once again, Kinzhal has demonstrated his tactical genius by scouting out Mogushestvo’s defences and destroying his entire air force in one move. Only chance does not factor into his calculations, but he claims that Angel acts as his good luck charm. While she doesn’t understand everything Kinzhal is telling her, Angel is nevertheless deeply in love with him.
Many centuries earlier, in the year 1812, Alexander Vishenkov prepares to ride off to face the French in battle. Before leaving, he confesses his love for his adopted sister Dusha and proposes to her. She does not accept immediately, but as a token of affection, she gives him her diamond locket, telling him that it will keep him safe on the battlefield. Her love for her family is reflected in her loathing for Alexander’s friend, Captain Victor Padorin, a notorious lecher who seems to have set his sights on Dusha’s two sisters, the natural daughters of Count Yuri Vishenkov. However, Padorin himself is deeply disturbed by his own feelings; he believes that he loves Irena, and does not understand why he is suddenly entertaining base sexual desires for the young and innocent Natasha.
In the 21st century, Bugayev admits to Trix that the pieces from the Vishenkov collection have a strange emotional effect on whoever views them; they were put on display partly to lure the art thieves out into the open, but also as an experiment to study their effect on the public. As he speaks to her, the return trip to OGRON HQ is brutally interrupted by an ambush from ordinary citizens who have found some other intelligence operating their bodies. In the ensuing gunfight, Vorman briefly recovers and forces Trix to drive him back to his camp outside the city, intending to kill her once they arrive. His internal injuries are slowly killing him, however, and when he begins to convulse, Trix takes her eyes off the road for a moment -- and nearly hits a beautiful woman on horseback, who has been waiting for them to arrive. Trix swerves off the road, hits a tree, and passes out.
Fitz is possessed by the same power animating his attackers and is forced to walk away from the convoy. The power then lifts from the attackers, but the traumatised survivors have no idea what drove them to act as they did. When Bugayev and his men search their attackers, live and dead, they find that each of them has half of an Imperial sovereign hidden somewhere on their clothing. Convinced that there is a connection to Vladimir Garudin, Bugayev decides to tap into Kronometr’s internal surveillance systems; if Fitz is inside the building, this will give Bugayev an excuse to launch a raid.
As the Doctor and Sund approach Sverdlovsk, they stumble across a bunker staffed by Alliance soldiers who have gone missing in action, and overhear them plotting to assassinate Kinzhal. The traitors spot the Doctor and Sund spying on them, but as they debate what to do with their captives, the bunker begins to grow warmer. The Doctor draws a connection between this fact, the fire in the Kremlin, and the fact that Sund’s determination to complete his mission has kept the dying man on his feet. When the Doctor deliberately provokes Sund into a fit of rage by insulting Kinzhal, the bunker bursts into flame around them -- or, more specifically, around the painting. The Doctor and Sund escape in the confusion.
Elsewhere, Kinzhal and Angel are confronted by an Sleipnir APC carrying Alliance soldiers on a mission to assassinate Kinzhal. However, Kinzhal’s unearthly confidence rattles his would-be assassins long enough for him and Angel to catch them off guard and kill them. Kinzhal and Angel then use the APC to return to General Wargaard’s base at Tobol’sk, where they report the success of the first phase of Kinzhal’s plan.
Back in 1812, Alexander is injured while fighting the French, but not as badly as he might have been. Padorin rides into danger to rescue his friend, but privately wonders whether he’s being selfless or whether he hopes to impress Irena. Aware that the French are going to win this battle and enter Moscow, Padorin takes the injured Alexander back to his family.
The power controlling Fitz marches him into the offices of Vladimir Garudin and releases him, and when he meets the man in person, Fitz realises that Garudin was the one controlling him. Garudin, the illegitimate son of a Russian prostitute, has clawed his way to the top of society by selling timepieces, and now that he’s had a glimpse inside Fitz’s mind, he has taken an interest in the ultimate timepiece -- the TARDIS. Garudin begins to torture Fitz for more information on the Doctor, and when his beautiful young secretary Tatyana protests, Garudin strikes her down, giving her a concussion. Shaken by Garudin’s brutality, Fitz claims that he’s terribly selfish and will sell out the Doctor if rewarded suitably, and the amused Garudin decides to show Fitz his operations so Fitz can decide what kind of reward he wants.
The Doctor and Sund reach Sverdlovsk, where they make contact with Colonel Gren de Schalles. Sund finally succumbs to his injuries, but de Schalles agrees to let the Doctor deliver the painting to Kinzhal on condition that the Doctor report back once he’s learned exactly what Kinzhal’s interest in the painting is. The Doctor thus travels to Tobol’sk, where he bursts in on Kinzhal’s audience with General Wargaard and demands that Kinzhal explain why he’s looting art treasures from the past -- especially a painting which seems to have the power to create physical consequences from strong emotions. Only Angel notices that Wargaard’s new aide bows her head when the Doctor enters, as if trying to avoid his attention.
Garudin shows Fitz to the lower levels of Kronometr, where disgraced physicist Harald Skoglund has constructed a private time machine for Garudin -- the Misl Vremnya, “Thought Time.” Every individual moment in Time is connected to its neighbours by a thread of binding energy with a certain elasticity to it; the Misl Vremnya uses that energy to allow clairvoyant travel along an object’s timeline, allowing the operator to see through the eyes of anyone who has ever come into contact with the object. If the operator’s will is strong enough, they can even control their host’s body. The people who attacked the convoy had half-sovereigns hidden on their persons; the other half of each sovereign is connected to the Misl Vremnya, which is being operated by hired mercenaries. Garudin prepares to give Fitz a demonstration of his power.
Trix awakens to find herself in a beautiful Mediterranean villa on the planet Paraiso, the home of the woman she nearly ran down in the road. The woman, Aphrodite Diamante, has brought Trix and Vorman here so she may ask to borrow the locket, which she’s sought for a long time. Trix sees her mistrust mirrored in Aphrodite’s expression, but eventually hands it over and finds herself remarkably relieved by her own decision. Aphrodite drapes the locket over a crystal vase in her villa, thus establishing a link along its timeline. By diving into the lake, the Espejo de Cielo, she and Trix are transported to the Vishenkov home in 1812 -- where even Trix is moved by the tenderness of the reunion between Aphrodite and Dusha, her mother.
The reunion is also observed through Padorin’s eyes by Fitz and Garudin. Garudin has often used Padorin as a host, and he has become obsessed with the beautiful Dusha. He has also set his sights on young Natasha, and he hired his secretary, Tatyana, because she’s the spitting image of Natasha. Garudin leaves to deal with an emergency in the present day, but allows Fitz to remain, confident that Fitz is not disciplined enough to control another body through the Misl Vremnya. Meanwhile, Padorin retreats from Dusha’s righteous anger to drown his sorrows in vodka and to struggle with the demon of lust he sometimes feels within him, unaware that on those occasions he has in fact literally been possessed by the evil Garudin.
Aphrodite and Trix have introduced themselves as friends of Dusha’s original family, and the Vishenkovs welcome them in and tell tales of their beloved Dusha. Natasha claims that Dusha’s kisses have kept her safe from harm since childhood, and Alexander believes that her locket kept him alive on the battlefield. When Aphrodite gets a chance to speak with Dusha, however, she must ask her mother to take the locket back; as long as Dusha has the locket in this time zone and Aphrodite has the future version draped around the vase in her villa, Aphrodite will be able to return here for her. Dusha regretfully does as Aphrodite asks, though her request breaks Alexander’s heart. In turn, Aphrodite promises to remain long enough to ensure that the Vishenkovs reach safety before the time comes for Dusha to leave them.
Trix has been observing Aphrodite’s behaviour, and deduces that she is an emotional mirror, reflecting and amplifying the emotions of those around her; which, among other things, explains why Trix fainted from fear after nearly running Aphrodite down on the road. Armed with this knowledge, Trix manipulates Aphrodite into feeling enthusiastic about Trix’s plan to fetch the Doctor to help -- aided by the fact Aphrodite also knows the Doctor of old. Aphrodite gives Trix a strand of her hair, a genetic link which will enable Trix to dive into the nearest body of water and return to the Espejo de Cielo. But, rather than fetching the Doctor to help, Trix in fact intends to steal the future version of Dusha’s locket from Aphrodite’s villa.
Fitz returns to his own body and decides to check in on Tatyana, but on the way he encounters Bugayev and his men, who have seen him on the security monitors and broken in to retrieve him. Garudin pulls back his own guards, as Fitz still hasn’t realised that his kidnappers planted a sovereign in his clothing, and Garudin intends to use him as an unwitting spy in OGRON HQ. However, his plans go awry when Fitz convinces Bugayev to rescue Tatyana as well. Luckily, Tatyana has recovered with surprising speed, and she’s eager to help bring down her sadistic employer. She provides Bugayev with access codes into Kronometr’s computer systems, where they find evidence that the watches Garudin has supplied to prominent military figures across the world are linked to the Misl Vremnya. Bugayev can now justify raiding Kronometr to stop Garudin before he can activate his sleepers and take over the world.
In the future war era, the Doctor confronts Kinzhal, who also knows the Doctor of old but won’t tell him the details of their meeting. He does confirm that Dusha’s influence has turned the Vishenkov family’s belongings into empathic capacitors; the painting of Dusha amplifies strong emotions, which is why fires broke out around it when Sund was provoked. Kinzhal also confirms that he has adapted the enemy’s prototype time-travel technology and sent his soldiers into the past to collect artefacts which Dusha has been in contact with. Kinzhal himself is physically incapable of travelling through Time, as is Dusha; they are star-crossed lovers, sentenced to exile in two separate time zones by their own people. The Doctor realises that Kinzhal will never be at peace without Dusha, and that even if he defeats Mogushestvo, he will continue to wage war against the world simply to keep himself occupied. The Doctor thus agrees to adapt the transit belts’ technology to create a mental bridge between Dusha and Kinzhal so they can communicate once more. Kinzhal admits that a transit belt was lost in the 21st century and may have been retro-engineered into another time machine in that era, and the Doctor realises that he will have to use a transit belt to return to the 21st century, despite the risk that continued use of the transit belts will cause cumulative cellular damage even to him.
Kinzhal sends Angel to secure the traitors’ bunker which the Doctor found earlier, and Angel catches Colonel de Schalles helping the traitors to escape. Under interrogation, de Schalles claims to be acting for the cause of peace; Kinzhal’s allies have already realised that he will be without a purpose once Mogushestvo is defeated, and fear that he will continue to wage war against the world. Nevertheless, Angel remains devoted to Kinzhal, though she knows that her love is not returned. Meanwhile, Mogushestvo sends his own army to raze Sverdlovsk to the ground, convinced that Kinzhal and Wargaard are preparing to attack Omsk now that they have scouted out its defences. Angel assigns de Schalles and his fellow conspirators to a position on the front lines -- the equivalent of a death sentence.
The Doctor survives his return to the 21st century, where he is picked up by Bugayev’s troops. Bugayev is disappointed when they meet, for this is not the same man he knows as the Doctor. The last time they met, Bugayev’s own arrogance resulted in his exposure to a temporal anomaly which caused him and his men to age unnaturally slowly, but the Doctor’s evident compassion when Bugayev tells him this convinces Bugayev that this “Doctor” is also trustworthy. When the Doctor meets Tatyana, he recognises her as the spitting image of Angel Malenkaya, and when Fitz reveals that she also resembles Natasha Vishenkov, the Doctor decides to return to 1812 to meet Dusha in person and find out what Kinzhal hasn’t been telling him. But Garudin is watching all of this through Fitz’s eyes, and once he gets the chance, he manipulates Fitz into transferring the half-sovereign from his clothing and into the Doctor’s, intending to seize control of the Doctor’s body as soon as an opportunity presents itself.
The Doctor travels to 1812 and speaks with Dusha, who admits that she has no concrete memory of her past; however, she does remember being in love with someone, and she senses that the Doctor can be trusted to help her. The Doctor sees off the Vishenkovs, who intend to shelter in their country estate in Tushestorovo, and he and Fitz set off for Paraiso to confer with Aphrodite. On the way, the Doctor explains to Fitz that the zygma energy which binds individual moments of Time together can be harnessed via the Misl Vremnya to create a mental bridge between Kinzhal and Dusha. The Doctor believes that Dusha has the ability to twist probability in her favour, and that she has created a genetic link to Kinzhal’s time without realising it; the “good luck” kisses which kept Natasha free from harm as a child have also ensured that her descendants will be virtually identical and preternaturally lucky. But the existence of the Misl Vremnya in the 21st century, exactly what the Doctor needs if his plan is to succeed, is just a bit too lucky for the Doctor to accept at face value.
Meanwhile, Trix has returned to the Espejo de Cielo only to find both Kel Vorman and the locket missing. She theorises that Vorman recovered, saw her and Aphrodite use the lake as a means of transportation, and used the lake himself to return to his own time with the locket. She thus drapes Vorman’s abandoned transit belt over the vase and transports herself to his home time in order to retrieve the locket. However, her logic is flawed; Vorman did not know how the lake’s controls worked, and he in fact followed the women back to 1812, intending to force Aphrodite to help him return home.
The Doctor, Fitz and Aphrodite return to Paraiso, where they deduce what’s happened to Trix, Vorman and the locket. Aphrodite then must explain her nature to the Doctor, who is shaken to learn that Dusha and Kinzhal are two halves of the same being -- a Magellan, a creature like a sentient star. Aphrodite’s parents broke a serious taboo by giving birth to a child, and Aphrodite claims that the Doctor defended them at their trial; however, he has no memory of doing this, and realises that it happened either in his forgotten past or in his future. In any case, they were punished by being exiled to two separate time zones. Kinzhal is the intellectual side of the Magellan, and Dusha the emotional. The horrified Doctor realises that if Kinzhal and Dusha are put in mental contact as planned, their reunion will restore them to their original state -- and the Earth of the 51st century will be consumed in flame as the reunited Magellan absorbs the planet’s mass and energy to recreate its original form.
Back in the 21st century, Bugayev and his men storm the Kronometr building. Realising that his guards can’t hold back the attackers, Garudin shoots Skoglund and then himself, using the Misl Vremnya to transfer his consciousness out of his body as he does so. Bugayev orders his men to remove the historical artefacts from the Misl Vremnya and blow it up, unaware that Garudin’s discorporate mind is lurking in the lattices of zygma energy, waiting its chance to occupy another host body.
Back in 1812, the French enter Moscow, and a patrol stops the Vishenkov family before they can escape. Padorin, desperate to prove his good nature, tracks down his friends and attacks the French patrol, but is mortally wounded in the battle. Vorman then arrives, drawn towards Dusha by the attraction of his locket to its past self. He recognises Dusha from the painting and tries to kidnap her, believing that he will be handsomely rewarded for taking her to Kinzhal. When Alexander intervenes, Vorman shoots him dead -- and Dusha’s rage chars Vorman to a cinder and sets the entire street aflame. Blaming herself for Alexander’s death, Dusha sends the rest of her family to safety, but is then captured by a French patrol. In the confusion, a French soldier steals the future version of the locket from Vorman’s corpse.
The Doctor, realising that Kinzhal will continue his war in the 51st century unless he is reunited with Dusha, decides to continue with the original plan while he tries to think of an alternative. He thus sends Fitz and Aphrodite to back to 1812 to collect Dusha’s locket while he returns to the 21st century to set up the Misl Vremnya. However, as soon as the Doctor is alone, Garudin’s consciousness attacks, trying to possess him. The Doctor manages to fight him off long enough to find the sovereign in his pocket and discard it. Garudin senses his mind dissipating, and desperately transfers his consciousness into the first body he can find. Most of the artefacts have been removed from the Misl Vremnya, but one still remains, and Garudin finds himself within the body of the French lieutenant who has just taken Dusha prisoner.
Trix has transported herself into the middle of a war zone, where she is picked up by Colonel Gren de Schalles. Assuming her to be a deserter, he gives her a chance to redeem herself by helping him steal a psionic weapon which Kinzhal has retro-engineered from enemy technology. Trix successfully steals the weapon and infiltrates a platoon of time agents, with orders to deliver the weapon to de Schalles’ associates 200 years in the past; however, her behaviour attracts the attention of two other soldiers, and she’s forced to dispose of the weapon before she is searched. When she recognises the soldiers who have arrested her as Olrik Sund and Kel Vorman, she realises that she’s arrived in this time zone too early and that Sund and Vorman have not yet been sent back in time to raid the Kremlin Museum. She gives them the slip, but decides not to contact de Schalles, correctly assuming that he intended to have her killed to cover his tracks once her mission was complete. Instead, she disguises herself and infiltrates the Icelandic Alliance’s forces, believing that if she waits long enough, the older version of Vorman will eventually show up again with the locket.
Bugayev’s men remove all of the artefacts from the Misl Vremnya, leaving Garudin trapped in his host body back in 1812. Over a month passes as the French army suffers through the devastating Russian winter, and Garudin is slowly driven mad by his host body’s suffering. Though Dusha seems numbed by Alexander’s death and the loss of her adopted family, Garudin has still been unable to break her spirit or take her beloved locket from her, and some part of him remains too awed by her beauty to take her by force. When he finds a French soldier bartering for food with a duplicate of Dusha’s locket -- the future version brought back to this time by Vorman -- Garudin kills him and takes the locket himself. But when he taunts Dusha with the locket, she snaps and stabs him to death with his own bayonet. Fitz and Aphrodite have also been stuck in 1812 for the past month, but when Dusha’s spirit flares briefly, Aphrodite is finally able to locate her. Aphrodite takes one of the lockets from her mother, and she and Fitz set off for the 51st century, leaving Dusha to wait for her reunion with Kinzhal.
The Doctor returns to the 21st century and explains the situation to Bugayev. Despite the risk that the world of the 51st century will be destroyed, Bugayev decides that this Doctor, like the one he knew, can be trusted to find an alternative. He suggests that the Doctor may be an alien who’s capable of changing his appearance, and the Doctor agrees that this theory bears consideration. In the meantime, Bugayev agrees to connect himself to the Misl Vremnya in order to bridge the gap between past and future -- and, on the Doctor’s advice, asks Tatyana to hold his hand for luck.
In the 51st century, Wargaard’s forces move in on Omsk, leaving Sverdlovsk undefended -- or so it seems. Though there’s no sign of Kinzhal’s forces, Mogushestvo sends his own army in to destroy Sverdlovsk, confident that they will be finished their work before Kinzhal can show his hand. But Kinzhal has buried tanks beneath the snow at Sverdlovsk’s intersections so they show no heat signatures until their modified engines fire, venting exhaust blasts of plasma fire hotter than the sun at the invaders. In Omsk, Mogushestvo watches in shock as his forces in Sverdlovsk are eliminated -- and Kinzhal’s forces then make their move on Omsk. The tanks were shut down and dragged across country by cloaked horses, and the movement thus did not register on Omsk’s heat-sensitive scanners until the tanks were practically within the city already. Omsk is overrun, and the defeated Mogushestvo vows to go down fighting. Meanwhile, de Schalles slips away from the front lines at Sverdlovsk and heads for Tobol’sk, aware that Kinzhal’s plan is succeeding -- which is why it’s so important that he be killed.
As Kinzhal, Wargaard and Wargaard’s aide observe the progress of the battle, Fitz and Aphrodite arrive at Tobol’sk, bearing the locket which will link Kinzhal to Dusha. The Doctor arrives and offers Kinzhal an alternative to the destruction of Earth. Due to the war, Earth currently has no space programme, but the Doctor can use the TARDIS to move Kinzhal through space but not time to an uninhabited planet which can serve as fuel for the Magellan’s reunion. However, Kinzhal considers even space travel in a time machine as being too risky, and since zygma energy is at its most elastic through the dimensions of Time, there is a good chance that the power of the Misl Vremnya will not reach to another planet. He thus rejects the Doctor’s plan, leaving no alternatives but the destruction of the world either by the reunion of the Magellan or by Kinzhal’s waging eternal war on its surface.
Angel arrives to report victory to Kinzhal, and overhears the conversation between him and the Doctor. At the same time, de Schalles and his followers burst into the war room to assassinate Kinzhal. Wargaard’s aide shouts out a warning, Angel takes a bullet while shielding Kinzhal from attack, and Aphrodite, responding to the emotions around her, attacks de Schalles and snaps his neck. Realising that she is dying, Angel offers to take Dusha’s spirit into her own body, knowing that Dusha will be able to heal the injuries; Angel will die, but her body will live on as a host for Kinzhal’s lover. Taken aback by this demonstration of selfless love, Kinzhal accepts this as a suitable alternative.
The Doctor identifies Wargaard’s aide as Trix, who infiltrated the Alliance as planned and has been waiting for the locket to arrive ever since. He assumes that Trix has been acting out of greed, but when she points out that they only became involved in this situation in order to get the locket, he concedes that he may have misjudged her. He hangs the locket around Angel’s neck and returns to 1812, where Dusha accepts the alternative plan offered to her. Dusha’s soul thus leaves her 18th-century body and passes through the Misl Vremnya into Angel’s body. The lovers are reunited; not in the way they’d anticipated, but Kinzhal is fascinated and moved by this new and strange kind of love -- not between two halves of the same being, but between two separate beings. He thus promises to spare the Earth, and offers to use the transit belts to establish an army of time agents who will police and protect the past.
The Doctor takes the past version of the locket from Dusha’s body and delivers it to Irena and Natasha in Tushestorovo, where they grieve for their lost friends and family but find strength in each other. In the 21st century, Bugayev destroys the Misl Vremnya, but the sensation of Dusha’s passing through Time has touched him, and he realises that he and Tatyana could easily fall in love; though he continues to age slowly, he need never be alone again. On Paraiso, the Doctor removes the diamond from the future version of the locket, intending to analyse it and learn the nature of the beings that have invaded the structure of the Universe. Fitz returns the empty locket to Aphrodite, who will live out her life, keeping the locket as a memento of her reunited parents.