The series opened with "A Mug Named Frank"; some months have passed since "A Fixed Address" and Marker is still living with Mrs Mortimer. She comments to him that his old problems are still present in Brighton—the police all know of him and of his record of being in prison. She also points out that, by his own admission, life has not been easy for Marker since he set up office on his own again and that he isn't getting much work. A chance encounter in a supermarket ultimately results in Marker making the decision to move to Eton. To emphasise this, the opening titles to the episode are those used for the Brighton series, whereas the closing credits play over a film of Marker walking around Windsor and Eton, as used for the rest of the series. The episode also introduces the new regular character of Detective Inspector Percy Firbank (played by Ray Smith)—a local police officer whose interest is piqued by Marker. The remaining 12 episodes of series 5 often explore the Marker-Firbank relationship in detail. Marker is very suspicious of authority figures, especially policemen, and Firbank—at least initially—considers enquiry agents to be a lower form of life. The two gradually come to like each other, even when their relationship is tested—the final episode of the series is "John VII, Verse 24" (29 September 1971) in which it appears Firbank is corrupt and is accepting money from known criminals.