The Doctor falls asleep in the interzone, apparently exhausted by his recent travails. The Kro’ka tries to wake him, but it occurs to Charley and C’rizz to wonder why he needs to -- and they realise that the Doctor can’t pass through the interzone barrier while asleep. This means that the Kro’ka can’t send him on to the next experiment, which must be irritating to the Kro’ka’s masters. The Doctor then wakes from a dream of a labyrinth and ringing bells, and although initially disoriented, he soon comes to the same conclusions as Charley and C’rizz and realises that he now has a hold over the Kro’ka. He taunts his tormentor, claiming to have worked out a great deal about the nature of the interzone, and when the furious Kro’ka tries to read his mind, he finds that the Doctor is now capable of blocking him. When the Doctor first arrived in this Universe, he was confused and disoriented, and the Kro’ka could enter his mind with ease; but he’s regained his wits, and his secrets will remain his own.

The furious Kro’ka storms off, leaving the Doctor and his friends alone in the interzone with no way out. But the Doctor begins to feel queasy, and realises that he fell asleep because he was suffering from time sickness -- which should be impossible in a universe with no Time. He places himself in a brief healing trance, and emerges refreshed and with a plan. Charley and C’rizz reluctantly agree not to interfere, whatever they see happen. Moments later, the Kro’ka returns, armed with a device that will enable him to peel away the layers of the Doctor’s mind to get at the secrets he is trying to hide. The Doctor collapses in pain when the Kro’ka activates the mind blast, but, as instructed, Charley and C’rizz stand by and do nothing. The Kro’ka tortures the Doctor with the mind blast, stripping his mental defences away one by one, and finally breaking down the final barrier and getting inside the Doctor’s mind... right where the Doctor wants him.

Too late, the Kro’ka realises that the Doctor tricked him into entering his mind and has now trapped him inside. For his part, the Doctor found the mind blast far less powerful than he’d expected, and he soon works out the truth; the Kro’ka didn’t actually have permission to do this, and it thus stole a low-grade mind probe to use on the Doctor without the Divergents’ knowing about it. The Doctor suspects that this isn’t the first time the Kro’ka has betrayed its masters, and he believes that things would not go well for the Kro’ka if they found out. The Kro’ka is sure that the Doctor would never condemn him to death by revealing the truth, but there’s a side of the Doctor that will do anything it takes to ensure his companions’ safety -- and if the Kro’ka doesn’t tell him what he wants to know, he’ll erase the Kro’ka’s memories of all his misdeeds, and sooner or later, he’ll be caught out in a lie that he’s forgotten he told.

Shaken, the Kro’ka reluctantly bargains his way to a compromise; fearing the consequences should the Doctor act on something only the Kro’ka could have told him, he will only confirm or deny things the Doctor could have worked out for himself. The Doctor thus learns that the TARDIS is still intact somewhere, and that the Divergents are running their experiments from a world called Caerdroia (“the fortress of many turnings”). The Divergents can track the Doctor anywhere in this Universe, due to the residue of Time he carries with him. Still bitter about the loss of his time senses, the Doctor presses the Kro’ka for further information on Caerdroia, but all the Kro’ka can or will tell him is that there is a castle there -- indeed, it’s everywhere on the planet. The Doctor eventually decides that he’s learned all he can, and turns the Kro’ka loose, threatening to tell the Divergents everything if he learns that the Kro’ka has lied to him.

One of the Doctors seems calm and rational; the second, short-tempered and insensitive; and the third, all over the place, fascinated by everything from the flowers to the cows and their tinkling bells. Charley concludes that each one represents an aspect of the Doctor’s personality; perhaps he was literally torn apart by moving out of a timeless zone into an area where Time is actively passing by. For convenience’s sake, she decides to refer to the irritable Doctor as Eeyore and the distracted, carefree one as Tigger. This established, the travellers climb a nearby hill to get their bearings, and the cows follow them, the loud tinkling of their bells doing little to improve the irritable “Eeyore”’s mood. There is a town in the distance, but no sign of the castle the Kro’ka claimed was everywhere in Caerdroia. The Doctor decides to seek out the people in charge, while Charley and “Eeyore” explore in one direction and C’rizz and “Tigger” in the other; they will meet in the town square in three hours.

C’rizz and the excitable “Tigger” find their way to a walled-off park, with a sign naming it as the Garden of Curiosities. C’rizz advises caution, but the Doctor rushes straight in for a look around. The first thing they encounter is a large, red, furry creature like nothing the Doctor has ever seen before, but after a moment he loses interest and darts off in another direction. Deeper within the Garden, they find a large rabbit twirling about in circles, and flowers similar to those from C’rizz’s home, though they are normally yellow instead of blue. The Doctor realises that C’rizz misses his home, but C’rizz claims to have accepted that he can never return. The Doctor is then distracted by the musical sounds of a babbling brook, but as he listens to it, the rabbit bolts in terror -- and C’rizz hears the snuffling, snarling, snorting sound of an obelat.

The Doctor wants to see the indescribable obelat for himself, but C’rizz insists that he leap into the brook and hide until it has moved off. Though disappointed that he’s missed the chance to see something new, the Doctor does wonder why a dangerous creature would be allowed to roam freely through the park. He and C’rizz emerge from the brook, and try to stay close to it while still following the path and keeping an eye out for the obelat. The Doctor keeps getting distracted by the fascinating flora and fauna, including something like a green hamster; he cheerfully admits that this aspect of him would be unbearable if it wasn’t mixed up with the others, and C’rizz forebears to comment. Eventually, the path and the stream go off in different directions, and the Doctor and C’rizz choose to follow the path on the grounds that it must lead somewhere. Indeed, it leads to a wall and a door out of the park -- and when they hear the obelat snarling nearby, they decide to pass through the door.

The calmer, rational Doctor finds his way to the town hall, which appears deserted but for a single clerk at the reception desk. The Doctor asks to speak to someone in charge, and the clerk gives him a confusing set of directions to the Visits Authorisation department. The Doctor eventually finds his way through the maze of corridors to the department in question, where the man on duty -- who is identical to the clerk at reception -- gives the Doctor an authorisation form and orders him to fill it out with a No.2 pencil, which he doesn’t have the authority to lend out. In order to get his own pencil, the Doctor will have to visit the Department of Communications Enabling Devices, or else he can borrow the clerk’s if he first gets a permit from the Department of Necessities for Daily Routine (Excepting Lavatory Paper). Weary of the bureaucracy, the Doctor asks the clerk if there’s anyone who can help him, and the clerk directs him to the Rhetorical or Genuine Questions Office for an answer to his question. When the Doctor reaches the Office, he finds that the clerk on duty is identical to the others. This clerk is at least willing to answer the Doctor’s questions, although he won’t lend out his No.2 pencil without a permit. Apparently, this town is governed by a mayor, but she is always out of the office whenever someone needs to see her. The Doctor gives up and asks the clerk the way out, and, after determining that this is a genuine and not a rhetorical question, the clerk directs him to a big green door marked WAY OUT.

Charley is not getting on at all well with the “Eeyore” Doctor, who is sullen and moody and given to casual insults. However, even he shows an interest when they find a gigantic cuckoo clock with no hands in the centre of the town square. Since this Universe has never had Time, the clock must have been constructed by someone from outside this Universe, or possibly by the Divergents. The Doctor and Charley climb the clock and slip inside when the cuckoo emerges, and find that the interior of the clock is indeed filled with clockwork. The doors shut behind them when the cuckoo pulls back inside, and they have little choice but to climb down through the gears, lighting their way with one of the Doctor’s everlasting matches. As they do so, however, the clock begins to chime -- and the gears begin to move.

The Doctor and Charley manage to negotiate their way through the moving clockwork to the ground, although Charley is nearly crushed when she risks jumping to another wheel instead of letting the Doctor catch her. He lashes out at her for her stupidity, but she realises his anger is born of concern for her safety; he may be the most unpleasant aspect of the Doctor’s personality, but he’s still the Doctor. As he only has one everlasting match left, he uses it to light a candle stub from his pocket, and he and Charley begin to search for a way out. The clock continues to chime, but in a strangely irregular fashion; however, the Doctor dismisses this as a secondary concern for now. He and Charley eventually find their way to a door in the wall of the clock’s cellar, and Charley holds the candle while the Doctor picks the lock.

“Tigger” is quite looking forward to meeting the monster, but the others would prefer to avoid it if possible. In order to do so, they must first work out whether they’re in a maze containing cul-de-sacs and dead ends, or a labyrinth, in which all corridors inevitably lead to the centre. Since the echoes make it impossible to determine the monster’s location, they have no choice but to pick a direction at random; fortunately, each of the Doctors is carrying a large ball of string in their pocket, which they can use to mark the way. As they walk, the “Eeyore” Doctor, irritated by his flighty “Tigger” persona, discusses the situation with the reasonable Doctor and concludes that there’s something not quite right about it all. But before they can determine exactly what’s wrong with this off-kilter world, they realise that the monster has fallen silent -- and before they can think of a plan, it leaps out at them from around the corner. The Doctors, Charley and C’rizz flee for their lives, but Charley got a glimpse of the monster before turning and running, and she’s recognised it as the classical Minotaur.

A man named Wayland then appears and leads the travellers to safety. Wayland explains that he built this labyrinth to protect the central computer terminal that regulates the day-to-day necessities of life for the city. However, the complex has been taken over by alien engineers who offered to help the people of the city only to infiltrate every aspect of their daily lives. They have placed the monster in the labyrinth in order to protect their secrets, and Wayland often visits it to look for people in need of rescue, as he now suffers the guilt of knowing that people have died in his creation. The Doctor and “Eeyore” agree to help him break through into the centre of the labyrinth, but “Tigger”, already bored, decides to return to the Garden of Curiosities for some fresh air. Charley and C’rizz accompany him, while Wayland leads the other Doctors to the mathematical lock that seals him out of the central chamber.

The Doctors agree to solve the equations, but as soon as Wayland has gone, they compare notes and conclude that the lock’s equations are transcendental -- which means that Wayland is trying to trick them into breaking into their own TARDIS. When they realise the truth and refuse to proceed, the Kro’ka gives in and addresses them directly. The Kro’ka was always Wayland, as well as the clerks in the administration building; he’s been trying to manipulate the Doctor into this position and trick him into opening up the TARDIS, so he can cover up his earlier mistake by presenting the TARDIS to his masters and claiming that this was his plan all along. He is not responsible for splitting the Doctor up into three aspects, but he believes that this has worked in his favour; now the dreamy, abstracted “Tigger” is on his own, and the Kro’ka intends to torture him for the secrets of the TARDIS, believing that this separate aspect of the Doctor will be easier to break. Before the other two Doctors can respond, the Kro’ka departs again, and the “central chamber” dissolves around them -- leaving them trapped in the labyrinth with the Minotaur.

When the “Tigger” Doctor, Charley and C’rizz return to the Garden of Curiosities, they discover that the signpost appears to each of them in their native language. The Doctor deduces that the signpost, like many of the other things he’s seen, is a construct created out of images from his and his companions’ memories. However, many of the other constructs have no purpose and are slightly off-kilter, such as the spinning rabbit, the wrong-coloured flowers, and the clock with no hands. The Doctor therefore concludes that they are side-effects of a process to create something else, possibly the labyrinth. It implies that they’ve been led into a trap, but if this is so, then the Divergents have more foresight than the Doctor had anticipated -- and if this is the case, why not simply take the Doctor by force? In any case, it implies that his other selves are in trouble, and the Doctor thus tells Charley and C’rizz to wait in the town square while he returns to the admin centre. When Charley protests, the Doctor ties one end of his ball of string to his belt and runs off, leaving a trail for her to follow.

Charley waits for a half an hour before deciding that the Doctor is probably in need or rescue once again. She and C’rizz follow the trail of string, but find it twisting about unpredictably -- and the town hall never seems to be in the same place twice. C’rizz tries asking for directions, and he and Charley discover that the people of this town are unable to perceive them consciously, although on some level they’re aware enough not to bump into them. Charley and C’rizz continue following the string, which eventually leads them to the town hall; however, the string leads them through a back window. Perhaps the Doctor broke in, or perhaps the hall’s architecture has shifted about and this used to be the front door. The two friends try circling around to the front hall, but when Charley tosses her empty candle-holder into the lobby, the floor opens up beneath it into a bottomless pit. She and C’rizz thus circle back around to the window and climb in. Once inside, they follow the string back to the lobby, but it stops there, leaving them with no way to find the Doctor. As they search the building, they discover that the architecture is indeed shifting around them, stairwells appearing on the ceiling or transforming into hallways or dead ends when they turn their backs for a moment. They eventually find a hallway full of doors; most of them lead to offices, one leads to a room full of lavatory paper, and one leads to a set of stairs...

The reasonable Doctor and the sullen “Eeyore” are still trapped in the labyrinth, and are being pursued by the Minotaur... which, when they stop to think about it, can’t have originated in this culture. This must mean that the Minotaur, like the maze, is a construct created from their minds -- which begs the question, what will happen if the two illusions interact? The Doctors thus stand up against the wall, and when the Minotaur charges them, they step aside at the last moment -- and the Minotaur pops right through the wall and ends up stuck on the other side. The Doctors then set off to search for a way out, and are unexpectedly reunited with Charley, who reveals that she descended the stairs into the labyrinth. All paths seem to lead to the labyrinth -- and, with a flash of insight, the Doctors realise that this means the labyrinth and the administration building are everywhere on the planet, just as the Kro’ka claimed was the case with the castle on Caerdroia. This is it.

The Kro’ka has strapped the “Tigger” Doctor into a machine designed to extract his memories through wires inserted directly into his brain. The Kro’ka admits that he admires the Doctor’s courage, but he must do what is necessary so the Divergents can gain the secrets of the TARDIS. The Doctor theorises that the Divergents are now putting into play what they’ve learned in their experiments -- the editing of memories they learned from Light City, and perhaps they split the Doctor into three personalities based on what they’d learned from Major Koth. However, when the Kro’ka informs him that the machine will simply extract all of his memories for the Divergents to peruse, the Doctor realises that this will include the Doctor’s memories of the Kro’ka’s misdeeds. If the Kro’ka turns over the Doctor’s memories, he’ll be punished for betraying and failing the Divergents; if he doesn’t, he’ll be punished for failing to deliver the TARDIS. Either way, he’s doomed, and the Doctor thus tries to convince the Kro’ka to set him free so he can defeat the Divergents. But instead, the Kro’ka decides to torture the Doctor for the information he needs instead of using the machine.

Before he can begin, the calm, rational Doctor arrives and reveals that he’s deduced the truth; this is Caerdroia, and the Kro’ka is carrying out his machinations right under the Divergents’ noses. The furious Kro’ka pursues the Doctor out of the lab into a chamber full of ringing, clamorous bells -- and he locks the Doctor into the room, where the volume and intensity of the bells threatens to drive the Doctor mad. As the Kro’ka sets off back to the laboratory, however, he is confronted by the third of the Doctors, the one Charley named “Eeyore”. But even she underestimated what this aspect of the Doctor is capable of. To the Kro’ka’s horror, this Doctor effortlessly invades his mind, just as the Kro’ka had tried to do to him earlier. Ordinarily the other parts of his personality keep his ruthlessness in check -- but they’re not here now, and there’s no one to stop him doing whatever it takes to make the Kro’ka tell him where the others are... Once he’s finished with the Kro’ka, “Eeyore” sets off to rescue the other two Doctors, and the terrified Kro’ka finds himself trapped in the labyrinth. As he flees, he encounters his true master and begs him for help. But Rassilon does not forgive failure easily, and what he does to punish the Kro’ka is even worse than what the Doctor did to him...

“Eeyore” rescues “Tigger” from the laboratory, and his better third is quite disturbed to realise what “Eeyore” must have done to find him. The two Doctors then locate Charley and C’rizz, and together they rescue the third Doctor from the chamber of bells. The disoriented Doctor reveals that the bells were ringing in code -- and he’s recognised it as a partial communication from the TARDIS. Finally, the Doctors realise that the TARDIS has been trying to communicate with them all along, but it was unable to convey the complete message through a single instrument, and it thus split the Doctor up so he could be in three places at once and receive all of the message. The chimes in the cuckoo clock, the babbling brook in the Garden, and even the cowbells in the field were all part of the message. The Doctors share their thoughts, put the message together, and discover that the TARDIS has given them directions to the heart of the labyrinth.