The Doctor, Charley and C’rizz emerge from the Interzone into a tranquil garden, but C’rizz suddenly collapses as the death of L’da plays out again in his mind. The Doctor realises that C’rizz desperately needs to relax and recover from the trauma of killing his lover, and the Kro’ka chips in, suggesting that the travellers visit the Multihaven, a city in which numerous religions interact peacefully. There’s nothing to stop them staying in the garden, of course... except for the Doctor’s curiosity. He and his friends thus make their way to the Multihaven, where they join the other pilgrims waiting to enter the city. The Bordinan’s assistant asks the newcomers to identify themselves, and C’rizz identifies himself as a member of the Church of the Foundation. As they will only permitted into the Multihaven if they belong to a religion, the Doctor and Charley identify themselves as Tourists, who worship C’rizz and begin each day with a cup of tea. C’rizz then faints, reliving the death of L’da once again, and the Bordinan’s assistant reluctantly allows the Doctor and Charley to jump the queue and take their ailing “god” to the Bordinan herself.

Elsewhere in the Multihaven, Bishop Parrash of the Kabari faith has been invited to the 23rd Church of Lucidity by Lann Carder, the head of the Lucidian faith -- the fastest-growing faith in the Multihaven. Carder’s disciple, Jebdal, hopes to convert Parrash, but the Bishop is committed to the worship of Kabari, a remarkably versatile product that can be used as foodstuff, a hat, or wallpaper, among many, many other things. It’s not a particularly spiritual religion, but Parrash is content to worship Kabari’s practicality. Jebdal nevertheless gives Parrash a tour of her church and shows him the “lucid crystals,” diamond-like crystals that she claims Carder physically harvested from the dreams of his followers. The sceptical Parrash is about to take his leave when Carder himself emerges from a wardrobe to greet him. Parrash is wary of the charismatic Carder, who claims that the energies of Lucidianism can literally change Parrash’s life, but reluctantly agrees to step into the wardrobe, which Carder refers to as the “lucidity accumulator.” To Parrash’s surprise, the wardrobe is larger on the inside. Carder claims that the lucidity accumulator contains the stuff of dreams, and that its interior is thus infinitely changeable. Bewildered, Parrash follows Carder down the corridor to see what lies at the heart of Lucidianism.

The Bordinan welcomes the Doctor, Charley and C’rizz to the Multihaven, and explains that her calling is to monitor the balance of beliefs and encourage diversity within the city. According to legend, the entire Multihaven sprang up around two children who met in the desert and engaged in a theological argument which more and more people began to join. At present, the city has a population of thousands and over 47 different practicing religions, including the Microbaptists, the Kabarians, the Divine Gas, and, now, the Tourists. Those wishing to enter the Multihaven must accept that their creed is only one of many, and must remain open to sharing ideas and discussions with the other religions. It’s the Bordinan’s job to monitor the conversion swings within the city and ensure that no one religion gets out of hand; and if any of the Multihaven’s inhabitants begin to believe too fervently in anything, a brief stay in the de-faith centre will turn them around.

The Doctor explains that C’rizz needs somewhere peaceful in which to relax, and the Bordinan happily guides them through the tangled, shouting crowds to the temple of the Bakoans. The Bakoans worship their own hymn, and never stop singing it, sustaining the song like an eternal flame. C’rizz can’t sing, but the Bakoan Basso-Profundo assures him that all he needs to do is listen; the hymn resonates on frequencies said to heal the spirit. The Bordinan assures the Doctor that the process is perfectly safe, and C’rizz admits that the hymn is already starting to soothe him. He decides to remain in the temple, while the Bordinan returns to the central office to keep her appointment with Bishop Parrash.

As the Doctor and Charley explore the Multihaven, Charley admits that she finds the Multihaven’s treatment of religion quite superficial, and the Doctor suggests that it’s been set up as another experiment, like the evolution chamber or Major Koth’s caves. At the moment, the Doctor is more concerned with C’rizz, whose mention of the Church of the Foundation has reminded the Doctor that he and Charley know little about their new companion’s past. His musings are interrupted by the familiar wheezing, groaning sound of his TARDIS materialising, but it apparently dematerialises again before he or Charley can locate it. Perhaps its chameleon circuit is functioning again, perhaps it is being affected by the different physical laws of this Universe -- or perhaps someone or something else is in control of the Doctor’s ship...

The Bordinan returns to the central office block, only to find that the normally punctual Parrash has missed their appointment. She has no way of knowing it yet, but Parrash is currently lost in the endless corridors of Lann Carder’s lucidity accumulator; he has been separated from Carder, and, looking for a way out, he instead enters the heart of the accumulator and encounters a crackling, glowing ball of light. The light burns into his mind, and as Parrash struggles to resist, a soothing female voice tells him not to struggle. Bishop Parrash has just encountered Miraculite...

The Doctor and Charley keep hearing the TARDIS materialising and dematerialising, but the Doctor can sense something terribly wrong with the sound, as if his ship has died and come back to haunt him. He and Charley return to the central office to ask for help, but find that the Bordinan has just received some disturbing news: in the absence of Bishop Parrash, over 1,000 Kabarians have converted to Lucidianism. When Charley suggests going to some of the religious leaders for help, the Bordinan tactfully tries to steer her clear of the Lucidians, piquing the Doctor’s interest. The Bordinan explains that the Lucidians believe that their god, Miraculite, gives them the power to reshape reality through dreams; the religion’s leader, a wise old man named Lann Carder, has been responsible for several minor miracles, but nothing that the Bordinan hasn’t seen before. The Doctor points out to the sceptical Charley that dreams do have a sort of power; even if they’re only electrical discharges in the brain, even electricity is a form of energy. And all power corrupts...

C’rizz wakes from his nightmarish vision to find Lann Carder and Jebdal tending to him in the 23rd Church of Lucidity. Disoriented, he confesses that he killed his lover for what he thought were the right reasons, but he now fears that he acted out of fear rather than compassion, and the guilt is driving him mad. Carder dismisses the Bakoans’ healing attempts as worthless, and offers to show him the true healing power of Miraculite; by this time, C’rizz is willing to try anything, and he agrees to step into the lucidity accumulator.

The Doctor tries to take Charley back to the Bakoan temple, but seems to have trouble finding it again, as though he’s starting to doubt his own sense of direction. Charley admits that she too has been feeling depressed lately. They do eventually find the Bakoan temple, but are startled to see that it’s been redecorated -- and more alarmingly, the never-ending hymn has ended. Inside, the Doctor and Charley find that the Bakoans have deserted their temple, which has been claimed by the Church of Serendipity. The Serendipitists worship Whoops the Great Neglecter, and praise accidents and chaos of all kinds; however, they are not responsible for the Bakoans’ disappearance, and have no idea where C’rizz might be.

C’rizz, lost in the endless corridors of the lucidity accumulator, meets Bishop Parrash, or what remains of him; the Bishop is now a whimpering, terrified shell of a man who can barely recall his own name. C’rizz decides to head towards the light, hoping that it will show him the way out, but Parrash tries to stop him, claiming that the light pulled a diamond out of his head. C’rizz dismisses Parrash’s babbling and heads towards the light, but it overwhelms him as he draws near, and he realises too late that he’s made a mistake. The voice of Miraculite speaks to C’rizz, urging him to step closer, and when Parrash tries to stop him from doing so, Miraculite blasts the Bishop into nothingness with a bolt of energy. However, even after seeing this, C’rizz is unable to resist Miraculite’s call...

Outside the accumulator, Jebdal is beginning to experience doubt. Why did Lann Carder send C’rizz into the accumulator instead of putting him in the hall of dreams with the other disciples? And where did the accumulator come from, exactly? Carder explains that C’rizz’s mind is full of doubt, confusion and guilt; he is thus a prime subject for Miraculite to transform directly. The accumulator is just an ordinary wardrobe that Carder found in a ruined house; however, he has stored inside it the energy from every lucid crystal ever harvested, and its interior is now a realm of pure Miraculite. Jebdal is appeased, and Carder thus leaves her in charge while he visits the Bordinan. The Bordinan isn’t terribly surprised when he reveals that he’s come to advise her to step down now, dignity intact, and allow Lucidianism to prevail within the Multihaven. This isn’t the first time that a religious leader has proclaimed the entire city to be theirs, and the Bordinan assures Carder that it won’t be the last. But Carder believes that Lucidianism will be the exception -- and he makes it quite clear that his “suggestion” was a not-so-veiled threat.

The Doctor arrives just in time to save Charley by overpowering C’rizz with his Venusian aikido. He and Charley visit the Bordinan for help, and she takes the Doctor to the de-faith centre to consult with Director Garfolt. C’rizz, recovering but still exhausted, can no longer recall exactly what happened to him in the lucidity accumulator. He apologises to Charley for what he did in his confusion, shaken that this is the second time in recent memory that he’s tried to kill her; however, Charley understands that he’s been through a lot recently, and assures him that he just needs time to recover. But like everyone else in this Universe, C’rizz doesn’t fully understand what “time” is.

Garfolt listens eagerly as the Doctor explains that the traumatised C’rizz has fallen in with the Lucidians. Garfolt admits that the “sleep rioters” are unlike any of his other patients; usually his patients are mired in dogma, but the sleep rioters seem to have burnt out completely, becoming untreatable shells of their former selves. Garfolt promises to care for C’rizz, but the Doctor becomes wary when Garfolt speaks enthusiastically of experimental new equipment and of putting C’rizz through a harsh regime of treatment to empty his mind of its extreme beliefs. The Doctor insists that Garfolt simply allow C’rizz to rest here and recuperate of his own accord, and Garfolt reluctantly agrees to the Doctor’s terms.

Lann Carder returns to the 23rd Church of Lucidity in a foul mood after his unproductive meeting with the Bordinan. More and more converts are arriving, and Jebdal, though happy that more are joining the Lucidians, is starting to become slightly concerned. Though Jebdal is devoted to the cause, she’d assumed that there would always be a few non-believers -- but it seems that the natural order of things is indeed changing, as Carder had always claimed it would. Carder enters the lucidity accumulator to commune with Miraculite, who informs him that the final harvest is about to begin. Carder must ensure that every citizen of the Multihaven takes their place in the Hall of Dreams, and he must fetch the Doctor, whose mind is more powerful than any other that Miraculite has ever encountered. The Doctor contains the dreams of several lifetimes, perhaps enough to increase Miraculite’s power to an almost infinite extent when it absorbs his lucid energy...

The Doctor and Charley leave C’rizz in Garfolt’s care -- and Garfolt wheels C’rizz into the treatment room, claiming that the Doctor has granted him permission to give C’rizz whatever treatment he deems necessary. C’rizz reluctantly allows Garfolt to hook him up to an experimental new monitor; when Garfolt connects himself to the monitor as well, he is able to see all the contents of C’rizz’s mind, including his deep senses of anxiety, guilt and remorse, and the near-complete lack of self-esteem. Garfolt then bombards C’rizz with a series of increasingly personal and abstruse questions, claiming that he’s trying to stimulate certain responses in order to open up and map C’rizz’s neural pathways. Once C’rizz is sufficiently disoriented and upset, Garfolt patches in the Opti-Mind Probe 3000, with which he can zero in on the undesirable mental accretions in C’rizz’s mind and bleach out all the negativity. There’s a mild possibility that this may cause brain damage, but so far nobody has complained. C’rizz is having second thoughts, but Garfolt has strapped him down, and he’s unable to escape as Garfolt switches on the probe...

The Doctor decides to visit the 23rd Church of Lucidity in person. Lann Carder is still inside the accumulator when they arrive, but Jebdal offers to give them a tour. The Doctor pokes around of his own accord and finds a cabinet full of lucid crystals, one of which shatters into nothing when he exerts pressure on it. In the Hall of Dreams, the Lucidian disciples are in a state of meditation, which is remarkably similar to sleep. Jebdal claims that they’re communing with the sacred visions of Lucidity; however, she admits that she hasn’t experienced the visions herself, as it’s her duty to convert others. The Doctor feels that she’s taking a lot on faith, especially when he learns that the lucid crystals are bright and crackling with energy when Carder removes them from the heads of the sleeping disciples, but solid, lifeless crystals after he takes them into the lucidity accumulator. The Doctor concludes that Lucidianism is not a true religion, but a scam to rob its disciples of their dream energy, leaving them as empty husks of the people they once were. He and Charley leave to warn the Bordinan, but on the way, it occurs to Charley to ask the Doctor what he saw when he went rushing off after the TARDIS. He sadly admits that he finally caught up with the ship just as it shattered into fragments, its temporal boundaries shifted catastrophically out of phase. It may have been an illusion created by the Divergents or the Kro’ka, but he fears that his ship truly has been destroyed.

In the central offices, the Bordinan’s assistant reports that the number of sleep riots is increasing; the Serendipitists’ shrine has accidentally been razed to the ground, much to their delight. The Bordinan requests that the heads of all major religions meet with her to discuss the situation, and is disturbed to learn that there no longer are any, apart from a few scattered cults and the Church of Lucidity. The Bordinan is still unwilling to exclude any religion from the Multihaven, but she’s starting to realise that she may have to make an exception.

Garfolt desperately tries unplugging the mind probe, but it’s too late; Miraculite is inside his mind now, and soon it has finished with him. C’rizz, now fully under Miraculite’s control, leaves to prepare for the final harvest, and Garfolt, babbling childishly, staggers to the Bordinan’s office and tells her that the patient he was bleaching pulled a diamond out of his, Garfolt’s, head. Disturbed, the Bordinan calls her assistant to have Garfolt taken away and cared for, but discovers that most of her staff are no longer in the building; they have all converted to Lucidianism. When even her assistant begins to repeat the Lucidian mantra, the Bordinan finally decides that things have gone too far.

Outside, the few remaining non-Lucidians are fleeing the Multihaven, having decided that it is futile to fight for their beliefs against Lucidianism. The Doctor realises that Miraculite has the power to generate self-doubt, which is why he and Charley have been feeling low lately; the stronger it gets, the more confused and depressed the people of the Multihaven become, and the more susceptible they are to the lure of Lucidianism. The Doctor realises that Miraculite was clouding his own judgement when he left C’rizz alone at the de-faith centre, but before he can send Charley to collect him, they see C’rizz standing on a platform nearby, preaching the way of Lucidianism to the crowd. At first, he doesn’t even recognise the Doctor and Charley, but when they heckle him, insisting that there can never be only one true way, he loses the flow of his speech and the crowd turns on him. The Doctor and Charley escort the dazed C’rizz through the jeering crowd as he tries to remember who he is.

Lann Carder emerges from the lucidity accumulator to find Jebdal having a crisis of faith; thanks to the Doctor, she’s beginning to question what really happens to the disciples in the Hall of Dreams. Carder explains that he’s storing the lucid energy from their dreams in the accumulator so it can later be released for the good of all -- but if this is the case, why is he taking away from them in the first place? The Bordinan then enters the church and presents Carder with a special order expelling the Lucidians from the Multihaven; so many people have converted that this edict will reduce the Multihaven to a ghost town, but the Bordinan is confident that things will eventually return to normal. Carder, unimpressed with the Bordinan’s decree, produces a crackling ball of Miraculite energy and demands that the Bordinan hand over control of the Multihaven; she refuses, and to Jebdal’s horror, Carder blasts the Bordinan with the Miraculite energy, vaporising her. It is time for the final harvest to begin...

The Doctor and Charley try to take C’rizz back to the central office, but find it in flames. The Doctor thus takes his companions to the Church of Lucidity to confront Carder in person. There, Carder has returned to the lucidity accumulator after ordering Jebdal to harvest the final batch of lucid crystals from the Hall of Dreams and then join him in the lucidity accumulator, but his cold-blooded murder of the Bordinan has shaken Jebdal’s faith, and she now realises she’s been living a lie. Believing that she genuinely wishes to atone for her mistake, the Doctor sends her to the Hall of Dreams to wake the disciples and get them clear of the Church. C’rizz remains weak and disoriented, and the Doctor thus places him in a light hypnotic trance and orders him to get some sleep. He and Charley then enter the lucidity accumulator to confront Carder.

Jebdal makes her way to the Hall of Dreams and tries to awaken the sleeping disciples, but even those few who respond to her just ask for a few more minutes’ sleep. Desperate, she tries shouting warnings that the building is on fire, but even this fails to stir many of the sleeping disciples. Inside the accumulator, Miraculite senses that someone is interfering with the final harvest, and the lucid energy within C’rizz’s mind possesses him, causing him to sleepwalk to the Hall of Dreams to confront Jebdal. The power of Miraculite gets inside her as well, threatening to turn her into a puppet if she does not obey of her own free will. The foreheads of the sleeping disciples begin to open up, and the voice of Miraculite orders the despairing Jebdal to harvest the emerging lucid crystals.

In the endless corridors of the lucidity accumulator, the Doctor and Charley apparently find the TARDIS waiting for them -- but the Doctor now knows it to be an illusion generated by Miraculite. Out in the streets, it was unable to fully manifest itself, but inside the accumulator, it’s solid and practically real. He and Charley try to enter it and dematerialise, just in case, but despite Charley’s hopes, the TARDIS fades away around them like a dream. They thus resume their search for Carder, and eventually find him -- and Miraculite. The Doctor promptly identifies the “god” as a bivarity anomaly quartz, a crystalline entity created by friction in the gaps between two realities. Somehow, this quartz slipped through the gap and entered this Universe, and it’s sustaining itself by feeding on the energies generated during REM sleep, presumably the closest thing this Universe has to the energies created by reality friction.

Miraculite begins to draw the lucid energy out of the Doctor; this close to it, he doesn’t even have to be asleep for it to feed. As a lucid crystal begins to push its way out of the Doctor’s forehead, however, the Doctor demands to know who Carder was before he encountered Miraculite and founded the Church of Lucidity. To Carder’s surprise, he realises that he can’t remember any of his past life before he “found” Miraculite -- and the Doctor reveals that Carder does not in fact exist. Miraculite dreamed him into being and sent him out into the world to bring new converts to it; only Carder’s belief in his own existence sustains him in this reality. As Carder loses that belief in himself, he fades out of existence, like a dream upon waking. Soon he has gone entirely, and without his belief to anchor Miraculite in a single physical form, the energy disperses. In the Hall of Dreams, Miraculite’s hold over C’rizz and Jebdal is broken, and as they recover, they see the glowing lucid crystals returning to the dreaming disciples’ bodies.