After the King of Ruthenia has been assassinated, Holmes and Watson are engaged to escort his son to Europe via Algiers, aboard a transatlantic ocean liner which also carries a number of suspicious persons, any of whom may be involved in a plot to also assassinate him.
| Directing | Roy William Neill | Director |
| Editing | Saul A. Goodkind | Editor |
| Writing | Arthur Conan Doyle | Characters |
| Writing | Leonard Lee | Screenplay |
| Production | Roy William Neill | Producer |
| Camera | Paul Ivano | Director of Photography |
| Production | Howard Benedict | Executive Producer |
| Costume & Make-Up | Vera West | Costume Design |
| Art | John B. Goodman | Art Direction |
| Art | Ralph Sylos | Set Decoration |
| Art | Martin Obzina | Art Direction |
| Costume & Make-Up | Jack Pierce | Makeup Department Head |
| Sound | Bernard B. Brown | Sound Director |
| Art | Russell A. Gausman | Set Decoration |
