The Prisoner S01E13 - Do Not Forsake Me Oh My Darling

Number Six is not himself. The Prisoner's mind is transformed in another man's body by The Village authorities in an attempt to track down a scientist, Professor Seltzman. When he awakes in his London home he has a tough task convincing people of his true identity, so he sets off for Austria to find Professor Seltzman - the only man who can help him.