The recap below contains plot spoilers about Episode 10: "Hammer Into Anvil" If you haven't seen "Hammer Into Anvil" yet, you can watch the full episode online.
No. 6 (Patrick McGoohan) swears to avenge the death of a girl (Hilary Dwyer) whose appeals for help when being persecuted by No. 2 (Patrick Cargill) are just too late for him to save her life.
In a community in which no one can be trusted, No. 2 is vulnerable to implanted suggestions that the Prisoner has, in fact, been brought to The Village to spy on him on behalf of his superiors.
No. 6 brings No. 2 to a state of increasing terror as he pursues his relentless policy. The one man he has need to fear for the success of his plan is No. 2's assistant, No. 14 (Basil Hoskins), who, if he had his way, would take sadistic relish in disposing of him. But No. 2 is scared of allowing his aide to take this drastic step.
No. 6 gradually builds up the impression that he is in touch with the outside world. He does it with gramophone records that may, or may not, contain coded messages. He inserts a strange advertisement in The Village newspaper that again might be a coded message. He uses a carrier pigeon for another message and many other means of indicating that he is reporting on No. 2.
In doing so, he puts suspicion on each of No. 2's most trusted servants. Each of them is dismissed in turn, eventually No. 14 himself. And as he does so, No. 2 becomes even more hysterical until he is finally in a state of complete mental and physical collapse.
Every man has his breaking point.