The Butler comes into Number Two's office and serves breakfast. The only other occupant of the room is a guardian sphere, seated in Number Two's chair. The butler rings a serving bell and a prior Number Two rises from beneath the floor. Irritable and on edge, he tests the food and then orders it removed. When the Butler ignores him, Number Two snaps out his request again, then tells him to remove the guardian sphere. He loudly declares that he isn't an inmate. He then calls his superiors and tells them that they used the wrong approach against Number Six, and they now have to do it his way or find someone else. He then switches on the monitor screen to Number Six in his flat. He snaps at the screen, asking Number Six why he cares, then calls Number Six and repeats the question. Number Six says he knows him. When Number Two repeats the question, Number Six says he'll never know. He hangs up and goes outside, angrily confronting a man with an umbrella. Number Six asks what his number is and the man nervously refuses to answer as Number Six rattles off numbers at him.
Number Two goes over the records on Number Six and calls his superiors to request permission to use "Degree Absolute". He informs them that they'll have to risk both him and Number Six, but it's the only way to find out why Number Six resigned. They allow him one week and he says that isn't enough time if they want to avoid "damaging" Number Six, but that is their final answer. He orders the Observers out of the Observation Room and then he and the Supervisor monitor Number Six as he sleeps. They use a wavelength generator on him, seemingly amplifying his brain waves to the point of danger. Number Two finally cuts off the treatment and informs the Supervisor that he has no choice but to undergo Degree Absolute.
That night, the wavelength generator, disguised as a lamp, is lowered over Number Six's sleeping head. Number Two enters the flat and starts loudly reciting nursery rhymes. Number Six doesn't wake up. The next morning, Number Two removes the device and tells a now regressed Number Six to get dressed and come along. The Butler places Number Six in a wheelchair and they take him to Number Two's office. They then descend through the floor and take a moving walkway to a large black-walled chamber, the Embryo, with a scattering of props and a kitchen within a cage.
Number Two sets the door lock for one week and seals the chamber. He says that they will now proceed through the seven ages of man, as written by Shakespeare. They begin with the Infant: Number Six is placed in a crib and the Butler shakes a rattle. Number Two presents himself as Number Six 's father and they play on a seesaw. When Number Two starts to probe for answers, Number Six abruptly leaps off the seesaw, leaving Number Two to tumble to the floor.
Next, the Schoolboy: Number Two is the teacher and summons Number Six to his office. He accuses him of talking in class and Number Six denies it, but admits he knows who was talking. Number Two demands to know who it is but Number Six refuses to rat on his fellow pupil as a matter of honour. Next is graduation day and Number Two praises Number Six for obedience and gives him his diploma. He then asks why Number Six resigned, and Number Six refuses to answer. They both scream at each other and Number Six tries to strangle Number Two. The Butler casually knocks him unconscious.
Next, the Athlete: They subject Number Six to further regression, but even in his childlike state he refuses to even acknowledge the number six. Number Six is a boxer and Number Two his trainer. He taunts Number Six into fighting back, saying he's the champ. Again he asks, "Why did you resign?" Number Six punches him and they switch to swords. Number Two now goads Number Six into killing. Number Six disarms him and threatens him with the blade, but refuses to stab him. Number Two accuses him of cowardice and asks if he resigned because of cowardice. Number Six refuses to answer and stabs the wall behind Number Two. Number Two pushes the matter and Number Six stabs him. Number Two notes he still can't bring himself to kill and Number Six apologises, and Number Two wonders if Number Six resigned because he was sorry.
Next, the Businessman: Number Six applies for a banking position with Number Two. As they have dinner, Number Two promises Number Six the job once he meets with the managing director. Number Two takes on that role and gives Number Six the job, but says that he will actually be doing top-secret work for the government.
Next, the Criminal: Number Six is arrested for speeding. He says that he was on a vital mission but Number Two, as the judge, finds him guilty when he can't explain whom he was saving. Again Number Two tries to get Number Six to acknowledge the number six, and again Number Six refuses. Number Six can't pay and places him in the kitchen cage, where he says he will appeal. Number two repeats the question and Number Six says he resigned for peace of mind. He demands to be released and Number Two puts a knife to his throat. Number Six dares him to cut his throat but Number Two notes that he killed during the war.
Next, the Soldier: Number Six and Number Two go on a simulated bombing mission. Number Two counts down to zero but Number Six again refuses to acknowledge the number six, causing them to miss their target the first time. The second time they succeed but are shot down. Number Two then assumes the role of a German interrogator and demands answers of Number Six, including why he resigned. Number Six simply rattles off numbers.
Number Six asks for supper and Number Two pauses to regain his energy. Number Six realises that Number Two has been trying to gain his trust, a necessary part of psychoanalysis and Degree Absolute. However, Number Two admits that if the doctor has problems of his own, the procedure is risky to him as well. Number Six begins to reverse their positions, asking Number Two why he doesn't resign. Number Two pours drinks and explains that the Embryo is used to conduct Degree Absolute, putting the patient through any and all of the seven ages of Man. The Embryo is self-contained and can sustain them for weeks. It is now only five minutes until time is up. Number Six closes the cage door, sealing Number Two in the kitchen. Recognizing the reversal, the Butler now obeys only Number Six. Number Six begins to count down the seconds as an increasingly desperate Number Two stumbles about. Number Six finally releases him with a minute left and Number Two collapses to the ground. He begs to explain why he resigned, then tries to strangle Number Six. Number Six easily shrugs off the attack and Number Two returns to the kitchen to pour himself more wine. The clock counts down to zero... and Number Two falls to the floor, dead.
Number Six checks his adversary's pulse and then looks up as the Supervisor comes in and congratulates him in on his victory. He asks what Number Six wants and is informed, "Number One." The Supervisor prepares to escort him out but first activates a door sealing off the kitchen cage. He escorts Number Six out, leaving the room dark and silent behind them.