The adventures of a Parisian boy and his little friends, who have taken on the role of detectives to track down the shady activities of Max, a disreputable individual who is courting Sylvie, the Parisian boy's young aunt... The discovery of a priceless necklace returned to its owner, will bring an upheaval in the destiny of little Jacky. "Born of an unknown father", at the age of twelve he finds an ignored home, a happier life in which his little friends will have their share, as well as Sylvie, who has got rid of Marx and will soon find a fiancé of higher rank.