Lieutenant Colin Race of the Royal Navy, busy investigating the tragic deaths of his girlfriend and another agent, is walking along Wilbraham Crescent when Sheila Webb runs out of number 19 into his arms, distressed. A middle-aged man is found on the floor of the house, stabbed to death. Poirot travels to Dover to help Race to establish whether Sheila is a murderer. Sheila claims she did not know the victim, nor even Miss Pebmarsh, a blind woman who owns the house. Miss Pebmarsh was not at home when the body was found, and she denies having requested Sheila's services as a secretary by telephone earlier that day.
Poirot observes the complications of the case, including an unidentified murder victim, four clocks stopped at thirteen minutes past four in the room where the body was found, and a host of neighbours who say they saw nothing. Race is determined to find the suspected German mole within the Navy who caused his girlfriend's death, and in a state of grief he becomes increasingly close to Sheila. A wall of evidence begins to build up against Sheila, and then another victim is found brutally murdered.
Amanda Peagram, a local landowner's daughter, is engaged to Roger Hall, and Lovejoy (on the instructions of Amanda's father) is furnishing a house with antiques for the couple. Unhappily, Amanda is not impressed, while Roger continues to play the field. At the wedding, Lovejoy overhears a row between Roger and Amanda's father and later finds Roger's body hidden in a suit of armour... but the body vanishes and nobody believes him. After the wedding, Roger is treated as a missing person. Lovejoy insists Roger is dead, but he can't produce the body - so he decides to investigate the murder and solve the mystery.