Crime novelist Roger Blackwood competes with hotel house detective Andy McCabe in solving a murder by poisoning at a medical convention.
| Actor | Role |
|---|---|
 Edmund LoweRoger Blackwood | Roger Blackwood |
 Victor McLaglenAndrew W. 'Andy' McCabe | Andrew W. 'Andy' McCabe |
 Rosemary AmesEleanor Blake | Eleanor Blake |
 Mary CarlisleOlive Temple | Olive Temple |
 Henry O'NeillMr. Claude Harvey | Mr. Claude Harvey |
 C. Henry GordonDr. John Mason Temple | Dr. John Mason Temple |
 William JanneyHarry Prentice | Harry Prentice |
 Charles Cahill WilsonAnthony Wilson | Anthony Wilson |
 John WrayFeets Moore | Feets Moore |
 John QualenOle | Ole |
 Herman BingHans | Hans |
 Madge BellamyTessie | Tessie |
 Robert GlecklerPolice Captain | Police Captain |
 Clarence WilsonGirando | Girando |
 Gino CorradoHeadwaiter | Headwaiter |