The temple of Shara on the planet Talderun is attacked by a fleet of corporate ships, and the high priestess Jal Dor Kal sends her witch-sisters into battle. On the fleet’s flagship, the Tempest, Commander Harlon detects the witches’ approach and knows that he and his men are as good as dead. Lieutenant Cochrane patches Harlon through to the CEO, Wendle Marr, who is preparing to address the board when his aide Tallis patches Harlon through. Harlon accuses Marr of sending men to their deaths; whenever possible, the witches are capturing the vessels intact, but Harlon knows that his men would be better off dying in space. Harlon signs off and evacuates with Lieutenant Cochrane, setting the Tempest to self-destruct behind him and hoping that the explosion will cover the disappearance of his escape pod. Marr orders Tallis to track down Harlon’s children and make them pay for their father’s disobedience...

The witches slaughter and feed on their captives as Jal Dor Kal cackles gleefully; the temple is safe, and somewhere out in time and space, the Other is coming, heralding the start of a new era. But Harlon and Cochrane have survived and have landed near the temple. Cochrane is upset about leaving her comrades to die on the Tempest, even more so when Harlon admits that the battle was all about control of the temple of Shara, an energy converter so powerful that its output was detected as far away as the homeworld. Wendle Marr will do anything to get that power, and as a result, Harlon’s men have been slaughtered. Harlon and Cochrane set off to search for survivors, unaware that they’re being observed by Archivist Yal Rom. He has been hiding on Talderun for two weeks, observing without interfering -- but if the newcomers get in his way, he has no qualms about eliminating them.

The Doctor takes Peri and Erimem to the Garazone bazaar, where he has business to conduct with his Pakhar friend Thesanius; the TARDIS’ telepathic circuits are overloading, and to repair them he requires certain equipment which the Time Lords frown upon. As Thesanius isn’t fond of humanoid females, the Doctor leaves Peri and Erimem to explore on their own, and advises Erimem not to call the Pakhars “rodent people” -- they consider it racist. The Doctor soon locates Thesanius and his gang trying to break into the local bank, and in exchange for the supplies he needs, he promises to remain silent. Garazone security guards arrive at Thesanius’ home as he and the Doctor finish their business, and as Thesanius ushers the Doctor out the back, the Doctor gives the grateful Pakhar a smoke grenade he can use to cover his own escape.

Erimem finds a blind Pakhar beggar chewing a sculpture out of a block of wood, and is oddly fascinated by the finished product, a demonic figure which resembles a centaur. The beggar, an ex-soldier, claims to have seen the demon himself during the wars in the Nekromanteia district. Erimem is fascinated by his description of the creature, a god of life and death, but before she can learn more, the Doctor rushes up and bundles her and Peri back to the TARDIS, steps ahead of bazaar security. Erimem requests that the Doctor set course for Nekromanteia, unaware as yet that the beggar’s mind was being controlled by Jal Dor Kal when he told his story...

The TARDIS telepathic circuits are still registering high levels of activity, as though the ship is being used as a relay of some kind. The Doctor suspects that Erimem’s cat Antranak, or rather the alien criminal inside Antranak’s mind, may be responsible, but that’s a question to be answered later. Now, despite the Doctor’s desire to visit the Olympic cricket match of the year 2060 AD, Erimem insists upon visiting Nekromanteia. She joined the Doctor in order to see other cultures, and something about the beggar’s story has deeply affected her. She gives the Doctor the sculpture of Shara which she purchased from the beggar, and the Doctor notes that the carvings on the side appear to be temporal co-ordinates...

The Other is coming, and Jal Dor Kal and her sisters raise their holy relic from beneath the amphitheatre in preparation. Yal Rom hides in the temple and watches as the witches pray to the skeleton of a giant centaur, perhaps the remains of Shara himself -- but to his surprise, the relic is throbbing with energy and a whinnying sound can be heard, almost as though the skeleton is still alive in some way. Outside, Harlon and Cochrane detect an energy surge from the converter, and prepare for trouble. Cochrane suggests getting away while they can and selling their information on the energy converter to the highest bidder, but Harlon knows that if they don’t give Marr what he wants, he’ll take out his anger on their families. Cochrane reluctantly accompanies him to the remains of the fleet, where they see witches crawling over the hulls of the ships, seeking the bodies of the dead. Harlon and Cochrane gun them down with surprising ease, and Harlon prepares to break into the ship and set it to self-destruct so his men can rest in peace, out of the witches’ clutches.

As Erimem lies bleeding on the floor, Harlon and Cochrane demand answers from the Doctor and Peri -- but Jal Dor Kal has sensed their presence, and she raises her sisters and sends them to avenge their own deaths. Gunfire no longer affects the already-dead witches, who snatch Peri out of away as she tries to help the Doctor carry Erimem to the TARDIS. Realising that he and Cochrane are outnumbered, Harlon remote-activates his ship’s transmat system, which locks onto all life signs in the vicinity and transports away Harlon, Cochrane, the Doctor, Erimem and Antranak... but not Peri.

Jal Dor Kal is satisfied with her work; the Other is safe, and Peri, the chosen sacrifice, has been delivered to the temple. Jal Dor Kal allows the bodies of her dead sisters to dissolve, their task complete, and sends Peri to the holy baths to be cleansed for the ceremony. Yal Rom has been observing all of this, and what he’s seen has confirmed his department’s suspicions; the relic is the central totem of the witches’ religion, and though its physical nature still evades description, this evening’s necromantic ceremony will provide Yal Rom with the perfect opportunity to learn more.

Wendle Marr is facing trouble back home. Although the Alpha Project on Challis Prime is nearly complete, Upper Manager Salaysian provides the board with evidence that Marr has achieved this by working his labour force like slaves. Additionally, the entire corporate fleet is missing, presumed destroyed, after carrying out a mission in the Nekromanteia district for Marr. Marr denies the accusations and accuses Salaysian of attempting to stage a coup, which by corporate law he is not permitted to attempt for another decade. The frustrated Salaysian suggests that the law should be changed, and realises too late that he’s gone too far. Triumphantly, Marr declares Salaysian in breach of his holy oath of office, strips him of his sash and has Tallis take him away for termination. The remaining Board members vote unanimously to allocate an additional 20 billion credits for the completion of the Alpha project. Satisfied, Marr visits Challis Prime and informs the workers that if they complete their work within a week, they will each receive a life pension, free education for their children, and food for the rest of their lives. The workers set to work with renewed vigour -- and Marr orders Tallis to execute them all once the work is done, and transfer the balance of the credits into Marr’s private account with a provision for herself.

While Jal Dor Kal and her witch-sisters prepare for the night’s ceremony, Yal Rom slips into the temple, recording all of his impressions in the log -- including the all-pervading stench of death. Elsewhere, the disoriented Peri hears Jal Dor Kal’s voice in her head, and weakly struggles to resist as the witches anoint her flesh with sacred oils. She is the sacrifice, chosen to bring “the Other” to the temple of Shara.

Harlon is amused by the Doctor’s optimistic belief that Peri is still alive, her life signs shielded from the transmat by the wrecked ship’s hull, and allows the Doctor to provide Erimem with a medical pack. Once he’s sure Erimem is recovering, the Doctor speaks with Harlon alone, adopting a bullying attitude and bluffing him into believing he’s an agent for the man who sent Harlon on this mission in the first place. Harlon explains that as the frontal assault failed, he intends to release a toxic gas into the temple, killing all of the witches and completing the mission alone. The energy converter which apparently makes the witches all-powerful, and which the entire battle has been about, also makes it impossible to use stun weapons inside the temple. The Doctor, appalled by Harlon’s ruthlessness, is even more disturbed by the readings he picks up from the temple; the energy converter is generating bizarre particles which seem to contravene all the known laws of physics. This is why Marr is so determined to get the energy converter for himself. In fact, although Harlon doesn’t know it yet, Marr is on his way to Talderun in person; he has another secret alliance, and he deliberately sacrificed the fleet by sending them in unprepared before the Board could fit the ships with more advanced weaponry...

Yal Rom finds his way to the preparation chambers, where he sees the drugged Peri being bathed and prepared for sacrifice. Though bound strictly to observe, not interfere, Rom can’t bring himself to stand by and watch this, and he thus breaks into the baths and frees her. Still disoriented but recovering slowly, Peri dresses and follows Yal Rom out of the baths. Their escape route takes them through the chamber directly beneath the amphitheatre, the mausoleum of Shara, where Yal Rom tarries to get a good look at the relic -- and finds that his hand passes straight through when he tries to touch it, as if it isn’t really there at all.

Erimem blames herself for the loss of Peri, since she was the one who suggested coming here. However, the Doctor suspects that she was influenced by whatever force was being channelled through the ship’s telepathic circuits. He needs to get a good look at the energy converter, which means getting past Harlon and Cochrane, who don’t trust him an inch. Erimem is still too weak to accompany him, but she agrees to create a distraction while he slips away. Following the Doctor’s instructions, she threatens to detonate a grenade powerful enough to destroy the entire mountain. Harlon realises she’s bluffing when he notices she’s still got her cat with her, but by this time the Doctor has gone. Harlon sends Cochrane to search for the Doctor, but this is at least partly so he can get Erimem alone. It’s been a long time since he was with a woman, and he intends to get his “dues” out of the company which betrayed him...

Peri and Yal Rom slip out of the temple while the witches are otherwise occupied. They don’t know what the witches are doing, however, until Peri mentions her friend the Doctor and Rom runs a scan to locate his life signs...

Cochrane returns from her fruitless search to find that Harlon has beaten Erimem half to death. As Cochrane berates him for his brutality, Peri and Yal Rom attack with gas grenades, stunning them and taking Erimem to safety. Though traumatised by her experience, Erimem fought Harlon off before he could do worse than beat her, and she vows to live with her pain. But Peri has bad news for her; Rom’s scan picked up only two male life forms on the planet, himself and Harlon. The Doctor is presumably dead. Erimem vows to honour the Doctor’s memory by putting an end to the evils of the witches and the honourless Harlon, and to this end, she and Peri throw in their lot with Yal Rom, who is now their only way off Talderun. In fact, Rom believes that their Doctor friend was an agent of a rival historical institution, and although he seems to have convinced Peri and Erimem to trust him, he’s prepared to kill them both if they get in his way.

Oddly, the Doctor is in the pavilion in the company of English coach Paul Addison, watching the famous cricket match at the 2060 Barcelona Olympics. Jimmy Harper is a first-rate player, but the Doctor isn’t quite sure how he got here, and he seems to recall being killed. Addison assures the Doctor that he was invited here, and suggests that he may be suffering from a touch of sunstroke; it’s easy to lose one’s head in the heat. The Doctor slowly begins to realise that all is not as it seems...

Harlon contacts Marr to negotiate for the data he’s collected on the energy converter. Before handing over the vital data, Harlon forces Marr to transfer payment into his secure account and authorise travel permits throughout the galaxy. Harlon then reveals that there are others on Talderun with an interest in the converter. Enraged that Harlon allowed himself to be tricked, Marr withdraws the travel permits and issues death warrants for his family, to be authorised if Harlon fails to remove the “rogue elements” from Talderun. Marr signs off, orders Tallis to book passage through the company wormhole to Nekromanteia, and then privately contacts Jal Dor Kal to warn her that the temple of Shara is still in danger. He’s already done his part to protect the temple, by sending in the fleet before they could be outfitted with more advanced weaponry and warning her of their approach. Neither of the allies trusts the other, but all appears to be going according to plan; Jal Dor Kal is confident that the witches will recover the sacrifice and deal with those who have desecrated Shara’s temple. The Other is close, and soon all will be prepared for the new era.

As the Doctor struggles to understand where he is, the cricket match finishes -- and starts over again. The Doctor and Addison are in a time loop of sorts, and according to Addison, the Doctor is dead. The Doctor refuses to play mind games, and, disappointed, “Addison” drops his guise to reveal that he is in fact Shara. Shara informs the Doctor that he is dead, his body destroyed and his life energy extinguished; he now exists only as a memory in this time loop, a discrete moment preserved in the Time Vortex for all eternity. The Doctor is appalled by the concept, which contravenes all the laws of temporal physics, but Shara assures him that he’s a welcome guest. In life, they were both explorers; in death, they can have all eternity brought to this one moment, and see everything there is to see.

Yal Rom supplies Peri and Erimem with weapons and leads them into the temple, where he fights off the witches while Peri and Erimem enter the mausoleum they found earlier. Antranak hides in Erimem’s bag, protesting, as she and Peri install signal boosters around the base of the holy relic; with these in place, the transmat on Yal Rom’s ship will be able to reach through the electromagnetic interference from the converter and beam the relic directly on board. Peri is starting to have second thoughts about Yal Rom, who carries an awful lot of weapons for an archaeologist, but Erimem points out that he’s unlikely to help them unless they help him in return, and they thus complete their work and trigger the transmat by remote control. The holy relic vanishes -- and as the tomb begins to quake and the witches shriek in terror and fury, Peri and Erimem realise they’ve made a terrible mistake. Yal Rom fights his way back into the mausoleum, but just as he arrives, rubble falls from the quaking roof and crushes the transmat boosters, trapping him, Peri and Erimem in the temple with the enraged witches...

Outside, Harlon detects the transmat activity and the energy surge, and deduces the truth; the witches’ relic must have been the source of power for the energy converter, and now that it’s been transmitted off-world, the power imbalance could destroy most of the planet. All Harlon cares about is getting the data Marr wants so he’ll have a bargaining chip, and he and Cochrane thus take off to search for the cloaked ship which Harlon suspects now contains the relic.

Yal Rom, Peri and Erimem are surrounded by the witches, and although Jal Dor Kal is initially too consumed by grief to order their deaths, this doesn’t last long. Yal Rom insists that he was justified in taking the relic away so it could be studied properly in a museum, but Jal Dor Kal claims to have lived with the relic for centuries thanks to the energy she absorbed from it, and although she worshipped it she also knew it for what it truly was. The witches take Antranak from the protesting Erimem, and Jal Dor Kal orders them to cut out Yal Rom’s tongue and bring it back for the cat to feed upon. Peri and Erimem are forced to watch as the witches cut out Yal Rom’s tongue and heart; Peri is horrified, but Erimem, while saddened, believes the witches are justified in punishing him for desecrating their temple, and that Yal Rom has paid the price for his crime. As the energy imbalance increases, the roof caves in, and Peri and Erimem are forced to flee, leaving Yal Rom’s body behind.

As the time loop collapses, Shara realises that he must restore the Doctor back to life so he can save the Universe by putting the relic back in place. Shara thus creates a new body for the Doctor and transfers his life essence back into it, out of this pocket of eternity. The Doctor is resurrected in the temple, and this time he manages to convince Jal Dor Kal to listen to what he has to say.

Harlon and Cochrane locate Yal Rom’s cloaked ship in orbit just as the Sentinel, Marr’s personal ship, emerges from wormspace. Marr orders Harlon to transmit the data he’s collected on the energy converter, but Harlon impudently signs off, hoping to retrieve the relic first and thus hold all the cards. Unfortunately, Marr detects the presence of the cloaked ship, concludes that Harlon is negotiating to sell his data to a rival, and orders Tallis to blow the cloaked ship out of the sky. Harlon’s ship is struck by debris and forced back down to the planet’s surface, and Marr follows, unaware that he’s just destroyed the source of the power he seeks... and that by doing so he may have condemned the Universe to destruction.

Shara and Jal Dor Kal both sense the destruction of the Relic, and realise that all is lost. The energy converter was designed to operate for eternity, and without the lodestone it will seek alternate sources of power. First it will consume the planet, and then the entire solar system -- and then the energy converter will fail, Shara’s bubble of eternity will collapse, and the entire space-time continuum will be shattered. This is what the witches have fought for centuries to prevent. The Doctor realises that they must replace the lost skeleton with another lodestone, and as Jal Dor Kal weeps for her lost opportunity, he realises that this is what she intended to do. She had summoned another being to become Shara’s familiar in this world, restoring him to life so she could take his place in a moment of eternity. But now her plans have come to nothing, and she is crushed under falling rubble as the temple collapses.

Outside, as the planet begins to tear itself apart, Marr and Tallis land to confront Harlon. Marr, interested only in the data cube which Harlon is holding, has Tallis shoot Cochrane dead and demands the cube, but Harlon threatens to throw it into the lava unless Marr explains why he’s sent so many people to their deaths. Marr admits that the Alpha Project is a duplicate of the temple of Shara; he and Jal Dor Kal have been working together so Marr can recreate Shara’s experiment and achieve eternal bliss. Harlon, furious, reveals that Marr’s own paranoia has already resulted in the destruction of the converter’s power source, and tosses the data cube into the lava, deciding that the universe is better off without such gods. Without the relic and the data which Harlon collected, the Alpha Project will be an expensive failure. Marr has lost everything, and, enraged, he orders Tallis to have Harlon’s family members executed. But instead, she decides that Marr is a lost cause and shoots him dead. She prefers to wield power behind the scenes, and as she and Harlon depart in the late Chairman’s ship, she suggests an arrangement which will enable her to continue doing so while Harlon becomes the new Chairman.