Number Two, whose plan involving the General and Speedlearn failed, nervously receives a call from his superiors. They want to know why Number Six resigned and warn that Number Two is not indispensable. After they sign off, he calls the scientist Number Fourteen and tells her they have to proceed with the experiment. She warns that it has only been tested on animals but he says they will go ahead with it tonight.
That night, a drugged Number Six is delivered to Number Fourteen's laboratory. Number Two is monitoring the experiment, and warns that she'll be in trouble if she allows Number Six to come to harm. She has three doses of a drug and prepares to inject Number Six with the one dose. For Number Two's benefit she explains that they can convert Number Six's brainwaves into signals that they can view. She gives him the injection and they watch as the same images of Number Six's resignation play over and over in his mind. Number Fourteen warns that they'll have only three attempts: a fourth dose will kill him.
Number Two believes that Number Six planned to sell out. He has three canisters of stored information representing the three likely suspects: "A," "B," and "C." He has Number Fourteen create a scenario featuring a party held by Madame Engadine, a Parisian hostess. She programs in the scenario and they watch as a stylishly dressed Number Six arrives at Engadine's party. Engadine greets him and he says that he's planning on going on holiday to think things through.
Number two has Number Fourteen feed in the data on "A," a spy turned defector who knows Number Six. "A" arrives at the party and attempts to learn what Number Six has planned for his new life. Number Six spars with him verbally and "A" asks what he has to sell. Number Six refuses to even acknowledge he has something to sell and prepares to leave. Number Two starts to panic, warning they need to find out what would have happened, but Number Fourteen warns that Number Six's subconscious directs the dream and they have no control over it. In the dream, Number Six tries to leave but "A" has his henchmen intercept him and they all drive out to a manor. Number Six attacks his abductors, knocking them out and taking great pleasure in punching "A" into unconsciousness. Number Two wants to move onto the next suspect but Number Fourteen says they need to give Number Six twenty-four hours to recover before the next drug injection.
Number Six wakes up the next day, fatigued from a poor night's sleep. He sees Number Fourteen outside buying flowers and vaguely recognizes her from the prior night despite his drugged sleep. He also notices an injection mark on his right wrist. He follows her to a cafe and spars with her verbally, talking about seeing her in a dream. She denies any knowledge of him and he accuses her of being one of "them." He then goes to the Green Dome and Number Two tries to get him to admit why he resigned. Number Six refuses once again and then flashes the injection mark at him. Number Two doesn't comment, leading Number Six to observe that an innocent man would have asked about it. After Number Six leaves, a nervous Number Two receives another phone call from his superiors and assures them he'll have the answer in two days.
That night, Number Six's maid serves him drugged hot chocolate. After passing out, he's brought back to the lab and the dream is restarted. Engadine asks about "A," who doesn't clearly remember the previous scenario. Number Two has Number Fourteen plug "B" into the scenario. At first "B" doesn't appear but a maid delivers a message to Number Six asking him to meet "B" in the arbour. Number Six goes there and finds "B," a female spy, waiting for him. They flirt and then dance, and Number Six warns her that her old enemy "A" was there earlier. "B" asks him about his holiday.
In the real world, a frustrated Number Two wants to accelerate the scenario as Number Six's resistance starts to burn up the drug. Number Fourteen reluctantly tries injecting her voice into the dream through "B"'s mouth. The process works and "B" says that the people after her want Number Six's information and might use her to get to him. He notes that such behavior is unusual for her and wonders if she's someone else. Two men arrive and Number Six easily defeats them. However, a third man arrives and holds a gun to "B"'s head, and demands the information. She begs Number Six to give up the information. Unconvinced, he demands the answers to several personal questions. Number Two fumbles for answers to feed into the dream and Number Six stalks off. It's clear that he wasn't going to sell out to "B."
The next morning, Number Six wake sup with a second injection mark. He secretly follows Number Fourteen through the Village and into the forest where she enters a hidden laboratory. He sneaks into the place through a ventilation shaft and finds his way to the laboratory. Viewing a replay of the party information and the three folders, he realizes what is going on. He finds the third syringe and dilutes the drug with distilled water, then returns to the Village.
That evening, Number Six dumps the drugged hot chocolate down the sink and fakes unconsciousness. Number Fourteen gives him the final injection but this time the dream is twisted due to Number Six's increasing resistance. He staggers around the party and Number Fourteen warns he may be dying, but a desperate Number Two orders her to continue. Number Six finally manages to get the distorted dreamscape under control. Meanwhile, Number Two prepares to feed in the data on "C," but admits they don't know who he or she is, as they never go anywhere except in disguise. "C" is known to attend Engadine's parties. Number Two hopes that Number Six knows "C"'s true identity and reveal it in the dream.
A blonde woman approaches Number Six and offers him a job, and she gives him an earring to bet at the roulette table. He wins and receives a key. Engadine approaches him with a matching key. Number Two realizes she's "C" and begins the procedure to bring her to the Village. However, Number Six and Engadine exit through a gate and the dream cuts out: the strain is too much on Number Six's body. Number Fourteen tries to revive him and warns that the experiment could kill him, but Number Two has to know what information Number Six was prepared to sell.
As Engadine drives Number Six through Paris, she explains that she is working for another person. Number two, surprised, admits that they never considered the possibility of a "D." Engadine drops Number Six off at a gate and he walks through it to find a masked man waiting for him on the other side. The masked man wants to purchase Number Six's information, but Number Six demands to know whom he's selling out to. Number Six glances around and then says that "they" must know who "D" is. "D" wonders who he's talking about but doesn't resist as Number Six grabs him and yanks the mask off to reveal... Number Two.
Numbers Two and Fourteen realize that Number Six is on to them. They watch the dream as Number Six walks through a doorway and back to the Village. He goes through the Village and enters the laboratory, where the dream Number Two and Fourteen look up. Number Six gives the dream Number Two the envelope containing the information he was supposedly selling: they're travel brochures. He lies down on the table in the dream and the images of his resignation flash over and over again. Number Two stares at the sleeping Number Six on the lab table... and the red phone rings for him.