Sir Graham Forbes, of Scotland Yard, often needs the help usually needed Paul's help with his latest tricky case. Myron Harwood, an American, is found dead in a country lane. Further celebrity murders follow. A common factor is that a note is left with each victim on a small piece of cardboard. On it is the inscription: 'The Marquis'. A private investigator named Rita Cartwright who is investigating the murders also ends up as a victim. It is time for Paul Temple to intervene after requests from both Sir Graham Forbes, of Scotland Yard, and the Home Secretary. But what can he do?