The Belgian detective Hercule Poirot investigates a series of murders in London in which the victims are killed according to their initials.

Tony Randall
as Hercule Poirot

Anita Ekberg
as Amanda Beatrice Cross

Robert Morley
as Captain Hastings

Maurice Denham
as Inspector Japp

Guy Rolfe
as Dr. Duncan Doncaster

Sheila Allen
as Lady Diane

James Villiers
as Franklin

Julian Glover
as Don Fortune

Grazina Frame
as Betty Barnad

Clive Morton
as Mister X