Charles Van Horn, son of rich and powerful Théo Van Horn, calls upon his former teacher Paul Régis to help him solve the mystery of his recurring bouts of amnesia.
| Directing | Claude Chabrol | Director |
| Writing | Frederic Dannay | Writer |
| Writing | Manfred Lee | Writer |
| Writing | Paul Gégauff | Writer |
| Camera | Jean Rabier | Director of Photography |
| Editing | Jacques Gaillard | Editor |
| Writing | Eugene Archer | Screenplay |
| Writing | Paul Gardner | Screenplay |
| Sound | Pierre Jansen | Music |
| Costume & Make-Up | Karl Lagerfeld | Costume Design |
| Art | Guy Maugin | Set Decoration |
| Art | Guy Littaye | Production Design |
| Costume & Make-Up | Jacky Bouban | Makeup Artist |
| Costume & Make-Up | François-Xavier Leclerc | Makeup Artist |
| Costume & Make-Up | Jacky Reynal | Makeup Artist |
| Costume & Make-Up | Alaine Scemama | Hairstylist |
| Production | André Génovès | Producer |
| Writing | Ellery Queen | Original Story |
