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 | Josep Maria Forn | Production Secretary |
| Costume & Make-Up | Antonio Turell | Makeup Artist |
| Costume & Make-Up | Práxedes Martínez | Makeup Artist |
| Sound | Ramón Ferrés | Original Music Composer |
| Camera | Mario Bistagne | Camera Operator |
| Costume & Make-Up | Pilar Campanales | Hairstylist |
| Writing | Julio Coll | Screenplay |
| Writing | Antonio Isasi-Isasmendi | Screenstory |
| Camera | José Luis Pérez de Rozas | Still Photographer |
| Editing | Pascual Bibian | Assistant Editor |
| Editing | Antonio Isasi-Isasmendi | Editor |
| Production | Miguel Grau | Production Director |
| Directing | Francisco Pérez Riba | Assistant Director |
| Camera | Federico G. Larraya | Director of Photography |
| Directing | Jesús Castro Blanco | Assistant Director |
| Writing | Julio Coll | Screenstory |
| Writing | Antonio Isasi-Isasmendi | Screenplay |
| Directing | Julio Salvador | Director |
| Writing | Julio Coll | Dialogue |
| Writing | Antonio Isasi-Isasmendi | Dialogue |
