French diplomat Dominique Auphal is put under surveillance by an unnamed secret service. They wish to find a weakness in his life in order to control him politically. Auphal becomes "File no. 51": his private life is spied, analysed and commented.
| Directing | Michel Deville | Director |
| Writing | Michel Deville | Writer |
| Writing | Gilles Perrault | Writer |
| Production | Philippe Dussart | Producer |
| Sound | Jean Schwarz | Music |
| Camera | Claude Lecomte | Director of Photography |
| Editing | Raymonde Guyot | Editor |
| Art | Noëlle Galland | Production Design |
| Sound | Joël Beldent | Sound Designer |
| Sound | Jean Pantaloni | Sound Designer |
