A man who is getting old,realizes how lonely he is and he decides to look for the sons he had with different women (hence the title=youthful indiscretions).So this is a movie made up of sketches ,with four segments,dealing with the four sons.The smug mediocrity of the first boy repels the old man who sneaks away. On the contrary,the second offspring is a very talented musician,brought up by his mother and his stepfather,with love and affection.The old man feels he is in the way and he exits. Unexpected twist :the third son was not his son,the mother had twelve (!) lovers at the time. Madeleine,his last lover ,had to sever all links with a family who was ashamed of an unmarried mother.So she decided to take care of a group of orphans .His son is among them,but when the hero comes to see her she does not want to tell him which one is HIS boy.