Bourgeois Parisian, Latin Quarter bookseller, Edouard Lestingois, (Charles Granval), rescues a tramp, Boudu, from a suicidal plunge into the river Seine, from the Pont des Arts. Boudu is brought into Lestingois' household. The family adopts the man and dedicates itself to reforming him into a proper middle class person. Boudu (Michel Simon) shows his gratitude by shaking the household to its foundations, challenging the hidebound manners of his hosts and seduces not only the housemaid but also Madame Lestingois herself. Gradually Boudu is tamed, shaved and given a haircut, and put in a suit. Then he wins a large sum of money on the lottery, and is guided into marrying the housemaid. Finally however, at the wedding scene, Boudu capsizes a rowing boat and floats away from the wedding party, and "back to his old vagrancy, a free spirit once more."
Source : Wikipedia