Unwed mother Sally Jupp meets Dalgliesh when her friend Stavros is murdered. Dr. Stephen Maxie makes his mother hires Sally as housemaid, but the rest of the household hates her. Dalgliesh tracks the drug ring Stavros was part of.

Sally blackmails her uncle for airfare to Venezuela. Stephen's engagement to Sally shatters the family. Dalgliesh narrows the suspects down to the one person missing when the victim was found.

Dalgiesh learns of Sally's attempt to blackmail Victor and her letters from Venezuela. Deborah is attacked. The Maxie family and guests start suspecting each other.

Adam Dalgleish has found circumstantial evidence involving the Maxie's daughter, Deborah, in the drugs and murder case he is investigating. Her brother is one of the suspects in another murder that took place in the Maxie's manor.

Deborah Maxie suspects her brother of killing his fiancee Sally and tells their mother. Dalgleish learns that Sally has been getting letters from Venezuela; her uncle confesses that he had been in her room the night she was killed.

Martha's venom spills out, and she admits having put sleeping pills in Sally's cocoa. A surprise arrives from Venezuela, and the two murderers of Dalgleish's two cases are brought to justice.