Edgar Wallace 
Number Six 

An international criminal arrives in London. Basically there’s the typical foreign bad guy, Caesar Valentine, who is suspected of many shady things but Scotland Yard, or any other police department for that matter, can’t pin any crimes on him so they send in an undercover operative only known as Number Six to find out enough to put Valentine away for good. The thing is nobody at Scotland Yard knows who Number Six is and neither does Charles Valentine! Along the way we meet Tray Bong Smith, a criminal low life who attracts the attention of Caesar Valentine, Stephanie, the beautiful daughter of Caesar, and Mr. Ross, a mysterious American millionaire.