When the body of actress Christine Clay, apparently strangled with the belt from a raincoat, is found dumped on a beach near her home, chief suspect is Robert Tisdall, a young friend of the actress who is seen running away from her body. Without an alibi and unable to prove that his raincoat is missing, his conviction seems assured when it emerges that he is a major beneficiary in the dead woman's will. Determined to prove his innocence but lumbered with an incompetent defence lawyer, Robert creates a diversion and escapes from the courthouse, catching a ride from Erica, the Chief Constable's daughter, who has earlier come to his aid when he fainted during his police interview. With Erica's grudging help, he hides out at an abandoned mill, until he is discovered by police and is forced to make his escape.
He and Erica head for a drivers' café in the hope of tracing the missing coat. They get caught up in a brawl, but not before they find out that the coat is now owned by a tramp known as Old Will, the China Mender. Before pursuing him, however, they must pay a visit to Erica's Aunt Margaret to allay suspicion. The aunt is suspicious, and after they have left she alerts Erica's father, who arranges for Erica to be intercepted by police. They evade the police, and Robert manages to find Old Will in a railway lodging house. They discover however that the coat is missing its belt, and without it their case seems hopeless. Old Will tells them that he was given the coat by a man with a blink. With the police in pursuit, the three flee to an old mine shaft, but Erica is captured when the shaft collapses.
Back at home, Erica, now convinced of Robert's innocence, is summoned by her father, who informs her of his decision to offer his resignation as a result of her abetting Robert's escape. That night, Robert visits Erica secretly to inform her of his decision to give himself up, but the discovery of a matchbox in the pocket of the coat gives a clue to the whereabouts of the real murderer.
Prompted by this clue, Erica and Old Will head for the Grand Hotel, hoping to find the blinking man, but Will attracts the attention of the police, who follow them in. They fail to spot the blinking man, who is blacked up and playing the drums in the dance band. However, he spots both them and the police, and assumes that they are on to him. Just as the police close on Erica and Will, the blinking man faints, and Erica, drawn by the commotion, rushes to tend to him. His blinking reveals his identity and he confesses to the murder. Erica and Robert are together again.
