The murder of well-known American Myron Harwood, found dead in a small country lane, heralds the start of a series of celebrity murders. Each time, the body is found with a small, square piece of white cardboard bearing the inscription 'The Marquis'.

When the eighth victim, a girl, is picked out of the river with the same card attached to her dress, a note from Paul Temple is delivered to Sir Graham Forbes. The message reads: 'Is it true what they say about Rita?' Rita Cartwright was a private detective investigating the Marquis murders - and now she too has ended up dead.

With the police baffled and the Home Secretary specially requesting his involvement, Paul Temple has no choice but to intervene...