During a voyage from Australia to Britain, Ronald Monteith is fascinated by fellow-traveller, Lionel Ventin. One sultry evening, shortly before arriving at Malta, Ventin tells Monteith the sensational story of his life - of his tragic second marriage... and of his vengeful first wife. When Ventin is found stabbed to death in his cabin, Monteith vows to find the killer. But he begins to regret his decision, when suspicion gradually attaches itself to the girl with whom he has fallen in love.