
The recap below contains plot spoilers about Episode 9, "Checkmate." If you haven't seen "Checkmate" yet, you can watch the full episode online.
Chess is a game of subtle moves, and No. 6 (Patrick McGoohan) wonders just what they are aimed at when invited to take part in an unusual game being played in The Village.
The chess board covers the whole of a courtyard. The chess pieces are human beings, their moves indicated by two men in charge, and No. 6 takes his position as the queen's pawn.
In such close proximity to the queen (Rosalie Crutchley), he is able to speak to her without attracting attention, and, as the game progresses, he talks about the possibilities of escape. She warns him to be careful, and her warning is emphasized by a move taken by the rook (Ronald Radd) on his own initiative -- the forbidden cult of the individual. It leads to him being taken off to hospital for treatment.
The game's umpire, the Man With the Stick (George Coulouris), takes No. 6 for a drink after the game and, in discussing the villagers, says their attitudes give away the differences between prisoners and their warders.
Working this out for himself, No. 6 realizes that the warders are impatient of any requests or comments, whereas the prisoners respond promptly. In this way, he feels, he can obtain a nucleus of people he thinks he can trust. The rook is one, despite the treatment he has received.
No. 2 (Peter Wyngarde) is suspicious and takes advantage of the obvious interest that the queen has been taking in No.6 . A new treatment is tried out on her, implanting in her brain the belief that she is in love with No. 6 and that he is in love with her: that she will do anything for him, even betray him to save him from his own folly. She is given a necklace that she is told is a gift from No. 6 -- a necklace with a bugged detector-transmitter in the locket.
The queen follows No. 6 everywhere, hopelessly in love with him, and the detector keeps the watchers informed of their whereabouts, until No. 6 stumbles onto the secret and makes use of the components to help make the radio he needs for an escape bid.
He has now assembled those he can trust. The climax is reached when they get to a motorboat, and in this world of suspicion No. 6 finds that the one man he cannot trust is the one he has trusted the most simply because that one man could trust no one, not even No.6 .