Number Two uses a double for Number Six in a complex plan to make the Prisoner doubt his own identity. Removing a mole from his hand, brainwashing him into being left-handed, and impairing his fighting skills, they proceed to make him believe he's actually someone sent to replace the real Number Six while the Fake Number Six pretends to be him to his face.
This episode provides examples of:
- Face–Heel Turn: Number Twenty-Four, a young woman whom Number Six was helping test her psychic abilities, is in on the plot to convince Six that he's not who he thinks he is. It's revealed later on that she regrets it, and when she realizes that the real Six is trying to escape, she helps him.
- Gaslighting: Number Six is brainwashed to believe that he's a Village agent brought in to impersonate the "real" Number Six (who actually is a Village agent impersonating him) in order to break him.
- Heroic Willpower: How Six eventually regains his memories of being tampered with.
- That, and a few minutes zapping himself with a wall outlet.
- Hoist by His Own Petard: The Fake Number Six gets killed because Rover assumes that he's the real Six.
- Hope Spot: The real Six realizes that he can escape by pretending to be the Fake after Rover kills the Fake. Alas, he didn't know enough about the Fake's identity to get away with it.
- Identical Stranger: The episode screws with Number Six's sense of identity by secretly conditioning him to alter his reactions, then introducing an Identical Stranger who's been trained to react the way Six is supposed to.
- Inopportune Impersonation Failure: When his double is killed, Number Six tries to pretend to be the double so he can escape the Village. Unfortunately, Number Two happens to ask him about Fake Six's wife on the way out... and of course, the real Six has no idea about said wife and is forced to improvise. Unfortunately, the answer is wrong.
- Left-Handed Mirror: Played With. Number Two creates an exact double of Number Six and uses him to confuse Number Six into thinking that he's the double. The Villagers use aversion therapy on Number Six to turn him from right-handed to left-handed. The double is right handed, which he uses to claim that he's the real Number Six.
- Mind Rape: Number Six is brainwashed into believing that he is actually a Village operative assigned to impersonate Number Six.
- No-Holds-Barred Beatdown: Six delivers one of these to Fake Six after he regains his sanity.
- No, Mr. Bond, I Expect You to Dine: The Village subconsciously changes Number Six's favourite food to help make him think that he's someone else.
- No Name Given: Averted with Number Twenty-Four, who is identified by the given name Alison throughout, making her one of the only Village residents in the entire series to be referred to by name rather than by either a number or a title.
- The Reveal: This is the only episode where Rover is mentioned by name. It's actually at odds with some of the marketing (including the tie-in novels) that give it the name Guardian.
- Sanity Slippage: Six suffers some of this in the middle of the episode, starting to doubt his own identity.
- Ship Tease: The relationship between Six and Twenty-Four has become comfortable enough for her to reveal to him her given name, Alison, and for her to hang out at his place. No more than a tease, though, given that Six makes no attempt to escape with Alison, probably due to her Face–Heel Turn.
- Spot the Imposter: How Number Six's escape ploy falls apart; Number Two asks him about Fake Six's wife, and the real Six answers incorrectly due to not knowing the correct fate.
- Spotting the Thread:
- Number Two picks up on Six's impersonation of Fake Number Six fairly early, although he isn't too sure until Six fails to pick up on a clue.
- The real Six realizes that he's not imagining things when he notices a bruise growing and moving under a fingernail that had happened early on. It clues him in that he'd been sleeping - what he realizes was a prolonged brainwashing session - far longer than the passage of time that he's been told.
- Title Drop: The episode title is also the real password.
- Wham Line: "I am Six!" It is the first time Six ever refers to himself as his number instead of his name.
- "Susan died a year ago, Number Six."
