The Black Star (Vintage Mysteries Series). Johnston McCulley

The Black Star is a criminal mastermind who is pursued by Roger Verbeck and Muggs, a millionaire bachelor and his ex-thug partner. Black Star is a gentleman criminal in that he does not commit murder, nor does he permit any of his gang to kill anyone, not even the police or his arch enemy Roger Verbeck. He does not threaten women, always keeps his word, and is invariably courteous. He is always seen in a black cloak and a black hood on which is embossed a jet black star. The Black Star and his gang used «vapor bombs» and «vapor guns» which rendered their victims instantly unconscious.