Willy Ferrière is a gambler living beyond his means, and his mistress is as greedy as he's dead broke. One day, he says out of loud in a a Montparnasse café that he would give 100,000 francs to get rid of his wealthy aunt so he could claim his inheritance. Someone secretly lets Willy know it's a deal. The old lady is murdered, and a low-life criminal is manipulated to be the perfect suspect. But Superintendant Maigret feels something is wrong.
A moneylender kidnaps the young son of a rich widow as part of a plot to cheat her of her fortune. The boy is sent away on a fishing boat with the intention of drowning him, but a kindly old fisherman intervenes.
Jérôme Crainquebille, is an ageing vegetable seller who has sold groceries from his cart in in Paris for over 40 years. One day, he is harassed by a policeman who insists that he moves on. When he protests, Crainquebille is arrested, supposedly for swearing at the policeman.
