Barcelona, Spain. A young man is murdered in the middle of the street in front of the police headquarters. Miguel and Marcial, two agents of the Criminal Brigade in charge of the investigation, find in the victim's room a newspaper where a cryptic classified ad appears.
| Production | Miguel Grau | Production Director |
| Camera | Federico G. Larraya | Director of Photography |
| Editing | Antonio Isasi-Isasmendi | Editor |
| Costume & Make-Up | Antonio Turell | Makeup Artist |
| Costume & Make-Up | Práxedes Martínez | Makeup Artist |
| Directing | Jesús Castro Blanco | Assistant Director |
| Directing | Francisco Pérez Riba | Assistant Director |
| Camera | Mario Bistagne | Camera Operator |
| Production | Josep Maria Forn | Production Secretary |
| Camera | José Luis Pérez de Rozas | Still Photographer |
| Costume & Make-Up | Pilar Campanales | Hairstylist |
| Editing | Pascual Bibian | Assistant Editor |
| Writing | Julio Coll | Screenplay |
| Writing | Antonio Isasi-Isasmendi | Screenplay |
| Sound | Ramón Ferrés | Original Music Composer |
| Writing | Julio Coll | Screenstory |
| Writing | Antonio Isasi-Isasmendi | Screenstory |
| Directing | Julio Salvador | Director |
| Writing | Julio Coll | Dialogue |
| Writing | Antonio Isasi-Isasmendi | Dialogue |
