When the Duke of Denver learns his sister's fiancé is a card cheat, the engagement is broken and his subsequent murder's blamed on the Duke.

Winsey's search for his future brother-in-law’s murderer leads him to a farmer who's pathologically jealous of his younger wife.

Lord Wimsey investigates his sister's flirtation with Bolshevism and a romantic involvement with a Communist activist.

Lord Peter almost loses his life in the bog but is rescued and recovers in Grimthorpe farmhouse, where he stumbles onto some crucial evidence.

The Duke does not wish Mrs. Grimthorpe to be called as an alibi witness in his murder trial, but if Peter does not bring a vital piece of evidence, he will have to.