A fragment of a costume is the only clue when a man is killed at a masquerade ball.
When the nation's security is threatened, Poirot is called in to help find a stolen ruby.
Poirot is asked to help a woman who lives in fear of her husband.
Poirot falls in love and finds a criminal intellect that pushes his own to the limit.
Poirot is asked to solve a fictional murder, but then a real killing takes place nearby.
Poirot suspects that an old friend's son and his fashion-model girlfriend are in danger.