A recent widow has invited a group of family friends to her large and secluded country home. However, what the guests don't know is that the reason they've been assembled is that their host suspects one of them might be her husband's killer and she's intent on uncovering the identity of his murderer. As the guests begin to suspect each other, revealing long-kept and sinister secrets in the process, an unknown, black-gloved killer begins bumping them off in a variety of nasty ways.
Unfortunately the movie The Killer Is One of Thirteen is not yet available on HBO Max.
| Writing | Javier Aguirre | Screenplay |
| Directing | Javier Aguirre | Director |
| Production | José Antonio Cascales | Executive Producer |
| Sound | Alfonso G. Santisteban | Original Music Composer |
| Editing | Petra de Nieva | Editor |
| Writing | Alberto S. Insúa | Screenplay |
| Camera | Francisco Fraile | Director of Photography |
| Art | Eduardo Torre de la Fuente | Set Decoration |
| Costume & Make-Up | Carlos Paradela | Makeup Artist |
| Directing | Juan Antonio Arévalo | Assistant Director |
