The Spanish merchant "Mare Nostrum", captained by Ulises Ferragut, docked in September 1939 at the port of Naples to repair a breakdown. Walking through the ruins of Pompeii, Ferragut meets Freyra, an enigmatic and beautiful woman of whom she instantly falls madly in love, unaware that the girl is in fact a dangerous spy of the Third Reich.
| Directing | Rafael Gil | Director |
| Writing | Antonio Abad Ojuel | Screenplay |
| Writing | Rafael Gil | Screenplay |
| Writing | Vicente Blasco Ibáñez | Original Story |
| Production | Cesáreo González | Producer |
| Sound | Juan Quintero | Original Music Composer |
| Camera | Alfredo Fraile | Director of Photography |
| Editing | José Antonio Rojo | Editor |
| Art | Enrique Alarcón | Production Design |
| Costume & Make-Up | Armando Valdés Peza | Costume Design |
| Directing | José Luis Robles | Assistant Director |