Colonel March of Scotland Yard

A psychologist is found stabbed to death in a seemingly sealed room. Inspector March needs to decide who had the most reason to kill him, and how did they accomplish the task.

Colonel March's niece, a believer in spiritualism, thinks she hears her dead husband's voice and others in the house become convinced her husband has returned as a ghost. But has he?

A French fashion model asks for Colonel March's help, claiming a strange man is following her and she fears for her life. Several hours later she's found murdered, in mismatched colour, a telling clue for the inspector.

Members of the Himalayan Mountaineering Club are threatened by what appears to be the abominable snowman, and someone leaves a strange footprint on a ledge outside Colonel March's office.

While on holiday in France, there is a murder at the docks and Colonel March is asked by a friend of the French police to assist. The only clue left behind by the culprit, a sailor's cap - "looking for the head that fits this hat."

Two Mona Lisa paintings appear on the art market | but which one is the second original and which is the copy? Colonel March is determined to reveal the truth.