A chilling murder ruins a fun day at the races in the fifth historical mystery featuring Detective Chief Inspector Henry Johnstone.

1929. Police surgeon Dr Clive Mason is devastated when his wife Martha is found dead in an empty horsebox at Southwell Races, her handbag stolen. The Masons were enjoying a day out at the races with their friends, Dr Ephraim Phillips and his wife Nora, when Martha went to speak to a face she recognized in a crowd - and disappeared.

As Detective Chief Inspector Henry Johnstone and Sergeant Mickey Hitchens investigate, it's clear this wasn't a robbery gone tragically wrong - Martha was deliberately murdered. Why did the life of this well-respected, popular member of the community meet such a tragic end? Henry and Mickey soon learn that the Masons' marriage was not what it seemed, and make a number of shocking discoveries. Who was Martha Mason, and what secrets was she hiding?