Lionel Atwill
Erich von Rugen, alias Alex Morel
Regis Toomey
Capt. Clay Randolph [Chs. 1-6]
Virginia Christine
Countess Elsa von Merck, alias Trina Dressard
Eddy Waller
Doc Blair (as Eddy C. Waller)
Emmett Vogan
Count Manfried von Rinkton, alias Carl Lawton [Chs. 6-7]
Charles Wagenheim
Hugo Metzger, alias Abel Rackerby [Chs. 8-9]