 Charlie Oackley is the "Merry Widow Murderer", an evil strangler who seduces and kills rich widows. In order to be safe from the police he is going to his sister Emma who lives with her husband, Joseph Newton and her daughter Charlie. A detective is on the killer s track and arrives at the Newton s too, but before he can discover the truth, one of the suspected murderers dies in an accident and the police considers the case solved. Charles seems to be safe, but Charlie suspects him.