Romana is taking her leave of absence on the planet Davidia, a presidential retreat hired out to planetary leaders for summits, conferences, or just plain holidays; she has invited Leela along so they can discuss her decision to leave Gallifrey in more pleasant surroundings. However, they are still very different people; Leela takes in her surroundings on a sensual, instinctive level, while Romana is more analytical and intellectual. When Romana unthinkingly refers to Leela as an important asset, rather than as a friend, Leela takes offence and storms off. Meanwhile, their escort, Commander Hallan, unloads Romana’s and Leela’s belongings from their TARDIS and discusses the security preparations with Chief Steward Melyin, who remembers him from the last Presidential visit. Melyin has an alpha-alpha-plus security rating, which means that she has no family or friends who could be used to blackmail her into betraying her clients; to prevent her from being compromised, she cannot leave Davidia for the duration of her contract, but the compensation fees are so generous that she’s signed up for another ten years. Hallan only half listens to Melyin as she speaks, and appears completely oblivious to the fact that she’s flirting with him.
Romana visits Leela in her suite to apologise for her earlier remark. Leela is trying to open the window for some fresh air, and to her delight, Romana turns off the force field and throws a chair through the window, shattering it. Hallan responds to the alarm within seconds, but leaves, disgruntled, when Romana orders him to pay for damages and ensure that the window is not repaired. Leela admits that she appreciates the chance to relax, and she and Romana thus strike a deal. Tomorrow, Romana will accompany Leela out into the wilderness for a day away from all of the conveniences of modern technology; the next day, Leela will join Romana in the sense tanks, where they will be immersed in a semi-sentient water solution and experience the most restful sleep and dreams of their lives.
The next morning, Romana and Leela set out for a stroll in the wilderness, past stormy seas torn apart by Davidia’s six moons, two of which orbit in the opposite direction to the other four. Leela compares the stormy sea to her own turbulent emotions, but when Romana praises her poetic wisdom, Leela becomes pensive, claiming that wisdom belongs to the old. She and Romana then get into a bitter argument when Leela, delighted with the wilderness, praises the spirit that has designed it all. Romana points out that the fruits and animals all evolved through trial and error in competition and co-operation with one another, and is upset that such an intelligent person as Leela could believe in something as foolish as an intelligent design to the Universe. Leela storms off, leaving Romana alone in the wilderness, now certain that there is no place for her beliefs in Romana’s world.
As evening falls, Romana tracks Leela down by the fire she has lit to cook the wild boar she’s killed. Romana apologises for scoffing at Leela’s beliefs, though she does not share them, and gives in when Leela insists that they spent the night out in the open rather than return to the complex. As they rest, Romana reminds Leela of her earlier comment that wisdom belongs to the old. The Time Lords have active bio-fields to help them heal and regenerate, and as Leela has spent so much time on Gallifrey, those bio-fields have been interacting with her body, replenishing her own telomeres and preventing her from aging. If Leela leaves Gallifrey, that effect will cease, and Leela may age quite suddenly as the years catch up with her. Romana is reminded by this turn of phrase that her own past is catching up with her, but she’s found her place in life now as Gallifrey’s protector, and she refuses to let Pandora twist that to her own advantage.
Back at the complex, Hallan waits for his charges to return, upset that Romana appears to trust Leela over him. He does agree with Romana that Gallifrey should start participating in the affairs of the Universe, but unlike her, believes that they should be the ones in charge. Melyin stops by to offer him a drink and perhaps some company, but he fails to pick up on the cues she’s giving him, even when she shows great interest in the fact that Leela, an outsider, was able to marry a Time Lord. However, as Melyin becomes more and more obvious, Hallan finally realises that she’s making a pass at him, and despite himself, he is tempted. Before he can give in, however, a TARDIS materialises in the piazza, having somehow passed through Davidia’s security barriers using codes that should only be known to the President, her K9, and the security consuls on Davidia. When the occupant of the TARDIS emerges, there isn’t much of him left, and the horrified Melyin has him sent to the infirmary while Hallan sets off to inform the President.
Out in the wilderness, Leela admits that she’s beginning to wonder whether she can trust Romana. Andred has changed beyond recognition, and now that Leela knows that Romana has regenerated once before, she wonders whether her friend’s next incarnation will also be unrecognisable to her. Romana reminds her that she recognised the Doctor when they met again, but concedes that the Doctor was always a special case. At the same time, though Leela fears that the future will betray her, she also needs some form of closure before she can let Andred go. A spaceship then approaches their camp, and Romana is irritated to find that Hallan has disobeyed orders and come to fetch them; however, he insists that this is an emergency and tells her of the unauthorised TARDIS’ arrival. Its occupant is a Time Lord whose face and body have been burnt, his hands pulverised, and his tongue either ripped or bitten off -- and yet, despite his horrific injuries, he has not regenerated.
Back at the complex, Romana tries to make telepathic contact with the injured man, but fails, as his mind has been broken. Leela confirms that the “broken man” bit off his own tongue, and decides to mix a soothing balm for his skin using plants and herbs from the wilderness; again, she is offended when Romana insists that the man is already been treated with chemicals that have been scientifically proven to promote cell growth. Hallan has contacted Braxiatel, who speaks with Romana on the private link in her quarters and reports that the TARDIS in the piazza is also still on Gallifrey. Either the one in the piazza is an illegal clone of the original, or it is from the future, which means that the broken man’s traumatic experiences have not yet happened. The broken man has been injured in such a way as to make his identification impossible -- unless Romana interfaces with the Matrix, which would leave her vulnerable to Pandora. If this gets out, her political enemies will make capital of the fact that she is unable to do her job properly. Romana’s only option may be to force the broken man to regenerate, but she’s unwilling to do that until they know why he hasn’t yet regenerated naturally, and whether he came here of his own free will or not.
The next day, at breakfast, Hallan reports that the broken man has been showing signs of improvement -- and Leela points out that this started after she applied her herbal balm to his skin. Braxiatel has arranged for the broken man and the anomalous TARDIS to be collected from Davidia by the next supply ship, which will deliver him to a CIA special-ops TARDIS post in a nearby star system. Braxiatel will make a plausible excuse to visit the post and collect the evidence, hopefully without word getting out on Gallifrey. In the meantime, Romana will continue her holiday, and, as Leela had promised, today she will join Romana in Davidia’s sensory tanks. Once immersed in the semi-sentient, oxygenated water, they will be cut off from the outside world, and will experience the most relaxing dreams of their life. As an afterthought, Romana asks Melyin to set up a third tank for the broken man; his dreams may restore his sanity, and at the very least, he will be unaware of his suffering. Leela is somewhat wary of the tanks, but Romana assures her that nothing can go wrong...
Soon after entering her tank, Romana wakes in a panic, instinctively feeling that something has gone wrong. Leela emerges from her tank, calm and rational, and works out that she can free Romana by prying off the control panel and using her knife to trip the faulty solenoid. Somehow, Leela and Romana’s personalities have become jumbled together; Romana is operating on instinct and sensory input, while Leela is rational and analytical, full of knowledge with no understanding. A trail of watery footprints leads away from the empty third tank, and Romana and Leela set off to find Melyin and learn what’s happened to them. Romana finds that she can trace Melyin through her scent in the air, but there’s no sign of her outside; in fact, the whole complex is deserted, it’s dark, the ground is covered in snow and the skies are crossed with comets, which Romana regards as omens of evil. Romana’s knowledge is buried under layers of instinct, while Leela’s intuition has been smothered under knowledge -- but when Romana cries out for her friend Braxiatel, Leela recalls the private link in Romana’s quarters, and rather than waste time searching the complex, they set off to speak to Braxiatel in the hope that Hallan contacted him before the disaster. In Romana’s quarters, however, they find that the private link has been removed -- and the broken man is inside, again having used codes that only Romana should know.
Leela reasons that the sense tanks may have been moved from Davidia to a copy of the leisure complex, but when they test her theory by entering Leela’s rooms, they find that her window is still broken. Romana then senses movement in the shadows, and creatures like giant bats flock up to the complex and enter through the shattered window. Leela and Romana flee, carrying the broken man and pursued by one of the bat-shadows; neither can imagine what kind of environment could have naturally produced such creatures, which look like the products of an intelligent design. Romana’s TARDIS is gone, and there is thus nowhere to hide from the bat-shadows; however, though menacing, they do not appear to be attacking just yet. Leela and Romana flee out into the wilderness, but lose their way in the darkness, and as the broken man is slowing them down, Romana decides to cut his throat with Leela’s knife and force him to regenerate. The broken man seems to be encouraging her to do so, but when Romana cuts his throat, the bat-shadows swoop down upon him, and Leela and Romana realise too late that they were following the broken man all along. By forcing the broken man to regenerate, Romana has set the shadows free, and she realises that they are the shadows of a dark future -- shadows that have also been inside her all along.
Romana wakes to find herself inside her sense tank in the leisure complex, but she’s convinced that her experience was more than just a dream. She rushes off to find Melyin, and, to her astonishment, finds her locked in an embrace with Hallan, who has given in to temptation. Romana cuts through their embarrassed attempts to explain and questions Melyin about the sense tanks. As she’d suspected, the tanks are all fed from a central source. When Romana frees Leela from her tank, the shaken Leela confirms that she shared Romana’s nightmare. Romana realises that some of the herbs in Leela’s healing balm have hallucinogenic properties; the balm opened the broken man’s synapses, enabling his mind to interface with the semi-sentient water and share his nightmare with Romana and Leela, but because his mind was in such a jumble, their minds were jumbled together with his. Romana now apologises genuinely for scoffing at Leela’s beliefs; because she insisted on giving the balm to the broken man, he was able to communicate with them, and now Romana understands that there is a threat lying dormant within him, waiting to be unleashed at the moment of regeneration. In the dream, this evil took the form of bats, representations of an evil from Gallifreyan legend. Leela, still shaken but recovering, admits that she came to a better understanding of regeneration while sharing Romana’s analytical personality -- and when Romana vanished from the dream, Leela knew what it was to be truly alone in the dark. She thus decides to remain on Gallifrey after all, and hopes that perhaps one day Andred will be restored to her as he once was.
Hallan arranges for the broken man to be placed in temporary cryogenic suspension and transported to Haflon VII. Melyin tries to thank him for what he did, but he spurns her, ashamed that he lowered himself to dally with a short-lived alien. However, Leela arrives to pay her respects to the broken man, hears Hallan cruelly dismissing Melyin’s love, and punches him in the face. Melyin is thankful for Leela’s consideration but also amused, as she never really cared for Hallan; she’d signed on for another ten-year contract without considering the personal cost, but has wearied of working on Davidia and wants to get back to living a full life in the outside world. The only way to get out of her contract was to compromise her security rating, and she seduced Hallan in order to get caught on camera, hoping to take down the arrogant Time Lord a peg in the process.
Unfortunately, Braxiatel’s plan to pick up the broken man’s body without being noticed fails. Either someone on Gallifrey is keeping a close eye on him, they were tipped off, or they engineered these events in the first place. There is an alien pathogen in the broken man’s brain; it would be unleashed at the moment of his regeneration, which is why he has suppressed the instinct to do so, even though this will mean his eventual death. The future TARDIS has been placed in the anomaly chambers, Darkel has appointed herself the head of the inquiry, and Wynter and Narvin are arguing over jurisdiction; the broken man is a Time Lord, but the pathogen in his brain is alien, so both have a claim to the investigation. The two K9s have successfully sealed Pandora within the Matrix, so it’s safe for Romana to return to Gallifrey. For her part, Leela vows to find out who did this to the broken man and avenge his suffering, for his bravery has shown her that there are those on Gallifrey who still understand honour.