Peter Haddon plays Dorothy L. Sayers' amateur detective Lord Peter Wimsey in the Anglo-American . A scurrilous blackmailer is murdered by one of his victims, but it is innocent John Loder who is suspected of the crime. Making the casual acquaintance of Loder, Lord Peter Wimsey sets about to prove his new friend's innocence. It all takes place on a train trip from London to the English Channel, with Loder acting as bait to flush out the real killer. Dorothy L. Sayers wrote the original story for directly for the screen.