[1] It is the eighth in his series of novels featuring Inspector French, a prominent figure of the Golden Age of Detective Fiction.

Things dramatically change when Sybil confides to Anne that she believes her husband may be plotting to kill her, due to his desire to leave her for another woman.

He finds nothing at first to contradict the original police investigation's verdict of suicide and is about to abandon the inquiry when at the last minute he discovers a crucial piece of evidence that points to murder.

Now deciding that Grimstead and his lover have joined forces to murder his wife, he sets out to gather enough proof to successfully bring them to trial.

Believing he has cracked the case, French is about to arrest Grimstead when the solicitor is found shot dead in his study, again in a locked room: apparently a suicide, due to his remorse at the killing.