A mercenary named Banard escorts his mysterious but wealthy client to the forbidden planet of Demigest, only to learn too late that his client needed not a pilot, but a human sacrifice. There is a race to be run, and the client needs the help of Demigest’s monstrous inhabitants if he is to win it...

The planet Selonart is covered almost entirely with ocean, but for two large basalt islands -- and the water possesses bizarre frictionless properties, causing ships to move faster rather than slower. Every five years, the galaxy’s elite race across the surface of Selonart, and the time has come for the fourteenth regatta. Governor Marius revels in his own importance and toadies up to the corporate elite who are visiting his world, ignoring Administrator Peck’s attempts to inform him that the military submarine Gallant has failed to report back in after setting off to investigate an anomaly in the water. The presence of the strange Count Toriman de Vries does unnerve Marius a little -- but he still doesn’t know just how different this race is going to be...

Anji is extremely disoriented and angry; not only is she lost in space and time once again, following the disastrous events in Siberia she is now lost in an entirely different universe as well. The Doctor must find out how Sabbath intends to “fix” the problem before it’s too late, and fortunately or unfortunately Sabbath has left him a clue, a junk-mail model boat which generates a hologram advertisement for the Fourteenth Selonart Trans-Global Regatta. It’s clearly meant as a trap, but it’s also the Doctor’s only lead. Fortunately, despite his memory problems he recalls the regatta, which he may have participated in before.

The TARDIS materialises on the deck of a yacht, having homed in on one of the few solid places to land on the entire planet. The engines are racing, and there’s no sign of the crew at first -- until the Doctor, Anji and Fitz find the remains of a body strapped to the wheel. Nobody has responded to the ship’s SOS, and somebody has set its engines to overload. The Doctor goes to the engine room to investigate while Anji and Fitz search the ship for survivors. There is only one, a third-generation Selonart colonist named Bloom, a man with lumpen features and watery, innocent eyes. Bloom has been hiding in the yacht’s crawlspaces from the thing that slaughtered the other crewmembers... and he warns them that it’s still on the yacht.

The Doctor is unable to shut down the ship’s engines, and when he turns to leave he is attacked by a thing like a walking corpse. The monster pursues him to the upper decks, and catches up to him and his friends at the TARDIS -- but as the yacht races through the water at impossible speed, waves break over the deck, washing the monster overboard and the TARDIS with it. Bloom leads the Doctor and his companions to the lifeboat, and they escape moments before the ship explodes and sinks. Some distance below the surface, the water pressure gets to the nuclear reactors, and the shockwave from the ensuing explosion knocks Fitz out. When he recovers, two days later, he learns that the Doctor and Bloom have found strange crystals floating in the water. When Fitz touches one of the crystals he becomes dizzy, as if he’s seeing double, and then triple, and then quadruple. His perceptions return to normal when he drops the shard, but the Doctor suspects that this is only the tip of the iceberg, as it were.

For two days, the whole of Selonart has been without power, and things are little better once it returns. The cause of the failure remains unknown, the MikronCorps yacht is destroyed, and a repair crew is attacked and killed by a sea monster -- which should be impossible, as there are no native life forms on Selonart. The remaining yachts have docked safely as Beta Marina, but Marius is facing a PR nightmare, and when the Doctor and his friends are found he decides to use them as scapegoats and sentences them to death for the destruction of the MikronCorps yacht. The Doctor insists that he’s here to save the planet from a man named Sabbath, and something about his calm certainty gets through to Administrator Peck. Peck knows Marius to be a moron, and he has his own doubts about the enigmatic Count de Vries. Peck thus spends the night double-checking de Vries’ credentials, but unfortunately for him, de Vries catches him doing so...

Anji is upset when the Doctor concentrates more on the mysterious crystals than their pending execution. Bloom reveals that, like most “natives” of Selonart, can somehow sense the movement of the ocean. The Selonarts are normally ignored or treated as sub-human “Blockheads,” until the Regatta, when they are sought out for their ability to divine the currents. Bloom is the most talented of them all, and he was press-ganged aboard the MikronCorps yacht in the hope that his ability to find the fastest currents would give them an edge. He is unable to explain how he “feels” the water, but he does know that the ice felt like the water -- only more so.

Count de Vries presents Marius with what appears to be an Earth Central directive countersigned by Peck, ordering Marius to release the Doctor, Fitz and Anji. De Vries reveals that a man named Sabbath is planning to sabotage the race, and Marius concludes that de Vries must be an agent from Earth Central. By this time, the Doctor has grown bored waiting and has escaped, but while Fitz and Bloom get out of the building the Doctor and Anji are recaptured. Marius, however, apologises for the misunderstanding and sends them to the office block where de Vries is waiting to brief them. The Count is not there to greet them; instead, they hear a recording left by Sabbath, who has brought them here because he needs the Doctor’s help. He seems sure that the Doctor will be happy to do so once he learns the truth... but until then, the thing they encountered on the MikronCorps yacht will continue its work.

Fitz and Bloom evade the guards searching for them, and accept the help of a young blonde woman who offers to take them to a place of safety. Too late, they realise that the sadistic Valeria has press-ganged them to serve on the Bronstein People’s Union yacht Potemkin. Captain Levin is only interested in Bloom, but Bloom refuses to navigate for them if Fitz is killed, and Levin thus agrees to let him live -- for as long as the Bronstein yacht remains in first place. That night, as the crew prepare to set sail, Bloom tells Fitz more about his abilities. What none of the Earthers know is that Bloom is not a second-generation colonist, but a Third Jen -- and somehow, Bloom knows that his late mother has simply passed on from this world, and that they will be reunited one day.

As the Doctor and Anji ponder Sabbath’s message, they are confronted by Major Marleen Kallison of the Imperial Security Service. She is after Count de Vries, whose family background were discovered to be faked after he was spotted leaving a prohibited sector of space. The Doctor is appalled when Kallison admits that de Vries had visited Demigest, a planet of legend where some elemental, primeval force of evil twisted the human colonists into walking corpses who jealously guard their eternal “life”. The Doctor, convinced that de Vries is Sabbath, plans to find out why he is creating the ice formations in the water, and why he needs the help of the Warlocks of Demigest to do so. Meanwhile, the yachts set sail from Beta Marina for the next stage of the race, unaware that one of them has an extra passenger. The Warlock has survived the explosion of the MikronCorps yacht and is continuing its work...

The Doctor sets off with Kallison, telling Anji to look for Fitz and Bloom and convince Marius to call off the race before any more yachts are destroyed. Already, the yachts have reported spotting strange ice formations which are causing instrument failures and sensory distortion. The Doctor, convinced that the disappearance of the Gallant is related to these events, has Kallison search the area around its last reported location, and eventually locates a large iceberg. The Doctor and agent Warner descent to investigate, and find the Gallant -- or rather, several overlapping copies of it -- frozen into the base of the iceberg. Despite the Doctor’s warnings, Warner pushes forward to rescue the crew, and as he nears the iceberg he too splits into overlapping copies of himself and is swallowed up in the berg’s mass.

The Doctor barely escapes the same fate, and returns to Kallison’s vessel, where he warns her that they must get the planet evacuated. The destruction of the MikronCorps yacht has started a process of quantum chronometry, and the trapped sub’s nuclear engines are feeding power into the resulting “timeberg.” In an ocean, there are a near-infinite number of possible ways for a water molecule to move; here, all of the possibilities are occurring at once, and are locking up against each other as if in a temporal traffic jam. Hundreds of satellites are orbiting the planet, observing the regatta and passively flooding the ocean with radiation in the process -- and the combination of this radiation, the already bizarre properties of Selonart’s water, and the additional radiation from the yacht and the sub has started a chain reaction of temporal crystallisation which could consume the entire planet.

Marius has washed his hands of the conspiracy and has thus been ignoring Anji’s attempts to get through to him; however, he learns too late that this was the wrong approach when Selonart once again suffers a catastrophic power failure. This time, the visitors lose their tempers, and turn on each other in a riot of frustrated violence. Unlike the poor, who fear deep down that they’ll get caught, the rich have no restraints whatsoever when society collapses. Anji hides away from the violence in a bar, where she meets a native waiter named Arken who saw Fitz and Bloom being taken away. Arken recognises Anji as a friend of Bloom’s and leads her to a cavern deep beneath the surface of the basalt island, which the natives use as a secret hideaway from the brutal Earthers. There, Anji meets Bloom’s friend Whalen, and questions him about the cavern, which seems artificial to her. The Selonarts have little interest in their planet’s history, and the Earthers care for nothing but the race -- but Anji is beginning to wonder whether the strange planet Selonart can possibly have evolved naturally.

The Potemkin’s engineer is found in several pieces, and Levin orders Valeria to take Fitz into the hold to search for the killer. Fitz realises that the thing from the MikronCorps yacht is loose on this one as well. While searching they find something like a hollow urn, and Fitz, sensing an evil force emanating from it, refuses to go on. Valeria is impressed when she realises that Fitz is genuinely more afraid of the monster than of her. The Warlock gets past them and slaughters the rest of the yacht’s crew, and Fitz wraps the weird urn in a tarpaulin and takes it with him, believing that there’s some connection between the two. He is having trouble concentrating, and when he reaches the upper decks he sees that this is because the yacht has collided with a timeberg. Before the Warlock can kill Valeria, Fitz lures it away with the urn, and as it pursues him, trying to get it back, they fall onto -- or into -- the timeberg. The Warlock is trapped and absorbed by the infinity process, but Fitz and Valeria are rescued by Bloom, who seems able to navigate through the possibilities and back to reality.

Count de Vries finds Marius cowering in his office, aware that he will be used as a scapegoat for the disaster. De Vries tells Marius that this has all been a conspiracy by the natives, and directs him to the secret entrance to the natives’ hideaway. Marius rounds up a posse and sets off after the natives, unaware that de Vries, who is indeed Sabbath, is just getting him out of the way. Bloom, Fitz and Valeria are now prisoners on the Jonah, and Sabbath is just waiting for the Doctor to arrive. All seems to be going according to plan, apart from the death of the Warlock aboard the Bronstein yacht. Sabbath always intended to renege on their deal, but how will they react to the unexpected death of one of their own?

Kallison returns to Beta Marina to find the city in ruins. The Doctor stops Kallison from just blowing de Vries’ yacht out of the water, fearing this might make matters worse -- but he realises that she knows him to be Sabbath, and that her real mission is to kill him. Kallison belongs to a secret society which pledged to kill Sabbath after he threatened to “end history,” but the Doctor convinces her that first they must find out what he’s planning. He sends her out to restore order, but she realises that she’s compromising her directives and sets off with her only surviving soldier, Bloch, in search of weapons with which to kill Sabbath. However, the imperial yacht collides with a timeberg on its way back to Beta Marina and drifts into the harbour, bringing the crystallised time with it. As the ice begins to spread out around the island, Bloch begins to panic, and Kallison, barely hanging onto her own sanity, shoots him dead and continues on alone.

Whalen shows Anji ancient pictograms carved on the hideaway’s tunnels, and she realises that Selonart was artificially engineered. The entire planet was designed to change its inhabitants somehow, and it’s been having the same effect on the human colonists -- but what has it been preparing them for? Before Anji can come to any conclusions, they hear gunshots from the main cavern as Marius and his posse arrive and begin slaughtering the natives. Arken and some of the others give their lives to hold off the Earthers while Whalen, Anji, and most of the other Selonarts escape. Outside, they find that the entire island is “iced in” by the timeberg, but Bloom speaks to Whalen in his mind, assuring him that all is well.

Sabbath finds the Doctor in Marius’ office, apparently trying to build a device to screen out the effects of the timeberg. The Doctor is furious with Sabbath for engineering this disaster and getting a Warlock killed in the process. Sabbath, amused, switches on the Doctor’s alleged jamming device -- which explodes, killing him. The Doctor is disturbed to find that he’s less upset about murdering Sabbath than he should be, but nevertheless searches the body and takes the control unit for the Jonah. On his way out the Doctor encounters Kallison, who refuses to accept that Sabbath can be dead so easily and goes to the office to make certain. The Doctor leaves and is reunited with Anji in the streets outside, and when she tells him what he’s seen, he realises that Selonart was engineered to transform its inhabitants so they could transcend the limits of physical and temporal existence, thus becoming at one with the Universe without losing their individuality. Whatever Sabbath wanted from the process, all the Doctor can do now is shut down whatever is causing the communications blackout and get the survivors evacuated... but he’s afraid they’ve lost the TARDIS for good.

Marius emerges from the caverns to find that the island is now surrounded by ice, and realises that he was sent on a fool’s errand to keep him out of the way. He returns to his office to beg the Count for an explanation, and finds Kallison planting mines about his body, primed to explode as soon as her life signs are out of range. Marius shoots her dead in a fit of rage. Moments later, Sabbath revives as a side effect of his deal with the Warlocks. Realising what has happened in his “absence,” he transmats himself back to the Jonah, leaving Marius in the office as Kallison dies and the bombs go off.

Fitz, Bloom and Valeria are locked up in a cell on the Jonah. Fitz is growing concerned for Bloom, who seems to be growing less substantial somehow; however, Bloom assures him that he is simply becoming one with the ocean. Sabbath’s temporary death drives the savage ape crew mad with rage, and they head for the cells to tear their prisoners apart, but when they arrive Bloom transforms into a plume of water which washes the apes away. Fitz and Valeria flee, but on their way out they notice another of the strange urns hidden in a shadowy alcove... and this urn is sealed shut. On their way out of the Jonah they meet the Doctor and Anji on their way in, and although Valeria flees, Fitz remains with his friends. However, the Doctor has too much to worry about already and ignores Fitz’s warning about the weird urn. Irritated, Fitz decides to fetch it and show it to the Doctor, and by the time he realises that the urn is affecting his mind and forcing him to take it to the bridge, he’s unable to fight it.

The Doctor and Anji reach the bridge only to be confronted by Sabbath, who admits that, as the Doctor had suspected, he intends to seize control of the infinity process and gain the ability to manipulate the timelines. No mortal can make the calculations necessary to set the process in motion, not even Sabbath, which is why he lured the Doctor here -- and as he couldn’t be certain that the Doctor would track him down and agree to help, he released a Warlock to aid him in the meantime. Once he has control of infinity, he intends to renege on his deal with the Warlocks and erase their blight from the cosmos. However, once again he has misunderstood the nature of Time -- and of Selonart. It took three generations before the colonists produced someone like Bloom who is capable of surviving the infinity process; Sabbath can’t possibly handle it by himself. Worse, Sabbath has never heard of Major Kallison’s organisation, even though they vowed to kill him... because they never existed before. This timeline has become internally consistent, reshaping itself in ways too complex for a mortal mind to understand.

Sabbath refuses to accept that he’s wrong again, and activates restraints to seal the Doctor and Anji in place. He then sets the Jonah in motion, opens the urn he rescued from the Bronstein yacht and absorbs from it the life essences which the Warlock stole from the crews of the Bronstein and MikronCorps yachts. But just as the Jonah collides with the timeberg, the entranced Fitz arrives and opens the second urn, releasing a second Warlock which has been hidden on the Jonah all along. To Sabbath’s horror, the Warlock reveals that they never intended to honour their bargain with him; instead, they intend to seize control of infinity themselves, and remake the whole Universe in their twisted image.

Terrified, Sabbath identifies Fitz as the one who killed the other Warlock, but this Warlock simply slits Fitz’s throat and then turns on Sabbath. Sabbath has no choice but to release the Doctor, who opens the bridge’s portals, letting the infinity crystals pour in. Outside, Bloom is nearly ready to become at one with everything, but first he feels a friend crying out for help, and responds. The Doctor is thus given the power to choose and shape the possibilities around him, and with a wave of his hand he puts everything to rights, saving Fitz, confining the Warlock and restraining Sabbath. This is too easy and too tempting, and the Doctor thus tries again. This time around, Fitz snaps out of his trance just in time and fights off the Warlock. Sabbath releases the Doctor and Anji to help, but instead the Doctor opens up the portals, flooding the bridge. The Doctor, Fitz and Anji flee, but Sabbath is caught by the Warlock and drawn back into the urn, which implodes into itself and vanishes.