André Laroche, an industrialist, has just passed away. Face to his grave, as he is being buried, Anne de Vierne, the wife of a magistrate, confesses to her son François that Laroche was in fact Lupin and that he is his natural child. But he is not the gentleman thief's only offspring! Lupin had indeed another son by a housemaid, Gérard Dagmar, a dancer, magician and - occasionally - burglar. Which complicates the task of François who, to respect the last wishes of the testator, has gone in search of the treasure of Poldavia. For he keeps finding Gérard on his way and his efforts are constantly thwarted by his half-brother. Will Gérard prevent François from becoming the worthy successor to their father or will the two young men decide to join forces? That is the question.
| Directing | Édouard Molinaro | Director |
| Writing | Maurice Leblanc | Novel |
| Writing | Édouard Molinaro | Author |
| Sound | Georges van Parys | Original Music Composer |
| Camera | Pierre Petit | Director of Photography |
| Production | François Chavane | Producer |
| Editing | Monique Isnardon | Editor |
| Editing | Robert Isnardon | Editor |
| Art | Robert Clavel | Production Design |
| Costume & Make-Up | Georgette Fillon | Costume Design |
| Costume & Make-Up | Michel Deruelle | Makeup Artist |
| Production | Hubert Mérial | Production Manager |
| Directing | Pierre Cosson | Assistant Director |
| Camera | Noël Martin | Camera Operator |
| Art | Jean Fouchet | Title Designer |
