Mystery!: Campion - Season 2 (1990)

A second death occurs, that of Sutane's under-study, who had been playing the tricks on him to get out of the way so that he could take the lead role. Attracted to Sutane's wife Linda, Campion is not wholly convinced of Sutane's innocence until it is discovered that 'Squire' Mercer and Chloe Pye had once been a married couple and that she had come onto the scene to get back with him.

At the Golden Quill publishing house Paul Brand is at odds with his partners the Barnabas cousins - notably stuffy senior partner John - over publication of a rare manuscript by William Congreve. Then he is found murdered, locked in the firm's basement with a hose piping poisonous car fumes through a hole in the window. Michael Barnabas, a friend of Campion, is in love with the dead man's wife who, at the inquest, makes it clear that she and her husband were filing for divorce. Consequently Michael is charged with the murder.

Trying to prove his friend's innocence Campion makes several discoveries, including the fact that the murder was an exact copy of one in a book published by the Golden Quill. The dead man also had a mistress, who tells Campion that there was more than the one key to the basement and that Paul Brand had recently had one cut for himself. Plainly Brand was murdered because he had found out something about the William Congreve manuscript which somebody wanted keeping quiet.

Campion meets an American judge, while on a transatlantic cruise, whose life is being threatened by an enigmatic crime kingpin known as "Mr. Sinister."

Campion helps the threatened Judge Lobbett to disappear for his own safety and gives himself a chance to expose master criminal "Mr. Sinister."