The Ringer

A supposedly respectable man is forced to murder his lovely secretary when she finds out too much about his real business, which is white slavery (forcing women into prostitution). The girl's brother comes from Australia to find out what happened to her and goes on a rampage against the criminals, confounding the increasingly dismayed functionaries in Scotland Yard. Not only is he impinging on their turf, but they are unable to discover who he is. Meanwhile, he must evade not only the police, but the powerful criminals he is working against.