Prudence and Bélisaire Beresford have decided to take things easy. But when a rich Russian heiress disappears, Prudence can't resist and Bélisaire is forced onto the adventure. Their investigation will put them on the trail of a mysterious scientist who holds the secret to eternal youth...
| Actor | Role |
|---|---|
 Catherine FrotPrudence Beresford | Prudence Beresford |
 André DussollierBélisaire Beresford | Bélisaire Beresford |
 Nicolas MariéDoctor Nicolas Roscoff | Doctor Nicolas Roscoff |
 Agathe de La BoulayeDoctor Matarazzi | Doctor Matarazzi |
 Linh-Dan PhamMarie Van Dinh | Marie Van Dinh |
 Éric NaggarDoctor Jünger | Doctor Jünger |
 Bernard VerleyThe General | The General |
 Hervé PierreThe family doctor | The family doctor |
 Sarah BiasiniMarie-Christine | Marie-Christine |
| FFrançois BettensRudi | Rudi |
 Julos BeaucarnePrudence's father | Prudence's father |
| AAlexandre LafaurieHector | Hector |
 Katia TchenkoMiss Sakhaline | Miss Sakhaline |
 Marie-Christine DemarestThe Countess | The Countess |
 Ophélia KolbGisèle | Gisèle |
 Léa WiazemskyThe receptionist | The receptionist |
 Luc PalunA policeman | A policeman |
 Isabelle MigottoThe nude model | The nude model |