Aircraft are being shot down by a large black plane with a big "X" painted on the wing. The chief suspects are invited for the weekend to an old dark mansion.
| Actor | Role |
|---|---|
 John CarrollJerry Blackwood | Jerry Blackwood |
 Lona AndreHelen Gage | Helen Gage |
 John ElliottDoctor Norris | Doctor Norris |
 Henry HallHenry Goering | Henry Goering |
 Leon AmesCarl Goering | Carl Goering |
| WWillard KentInspector Gallagher | Inspector Gallagher |
 Pat SomersetCapt. Roland Saunders | Capt. Roland Saunders |
 Reed HowesLieut. John Ives | Lieut. John Ives |
 Wheeler OakmanLieut. Douglas Thompson | Lieut. Douglas Thompson |
 Gaston GlassLieut. Rene La Rue | Lieut. Rene La Rue |
| HHans JobyLieut. Baron von Guttard | Lieut. Baron von Guttard |
 Forrest TaylorSurvivor | Survivor |
| JJohn S. PetersLt. Baron von Guttard | Lt. Baron von Guttard |