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...

• Les Films Français
• Catherine Frot
• André Dussollier
• Nicolas Marié
• Agathe de La Boulaye
• Linh-Dan Pham
• Éric Naggar
• Bernard Verley
• Hervé Pierre