The colonel Daniel Blimp, of the secret British service, travels to Bangkok to investigate the murder of the Brittish Ambassador happened during a holiday in his residence. Blimp receives the help of Keats, agent of the secret service. Both men discover that the man who shot against the Ambassador is blind, and it takes the black skin as a result of a strange phenomenon of mutation.
| Costume & Make-Up | Juana de la Morena | Makeup Artist |
| Directing | Lina Romay | Assistant Director |
| Writing | Edgar Wallace | Novel |
| Directing | Jesús Franco | Director |
| Camera | Enrique Díaz | Camera Operator |
| Production | Antonio Mayans | Production Manager |
| Editing | Lina Romay | Editor |
| Production | Jesús Franco | Producer |
| Camera | Ángel Ordiales | Camera Operator |
| Writing | Jesús Franco | Screenplay |
| Sound | Jesús Franco | Music |
| Camera | Juan Soler | Director of Photography |