The Fioras jewels are missing and Francesca Lisle, one of John Mannering's (aka 'The Baron') neighbours, is mysteriously asked by her father to retrieve a leather holdall from underneath the floorboards and take it to him at Waterloo station. Francesca is kidnapped, however, and ends up in the River Thames. Meanwhile, Joy Lessing, is also kidnapped, or so it would seem ... Mannering is unwittingly involved and sets off to investigate, but cannot tell the police everything he discovers and so acting almost alone must somehow outwit the other players in a complex plot of deceit and duplicity, including having to deal with the notorious Ephraim Scoby.