Suivez cet homme

Two investigations:1)In a seedy house on the wrong side of town ,in a place with mildewed walls ,there lives a pawnbroker .Her apartment is packed with valuable stuff.One day,she's poisoned and there are two suspects : her husband she left and who,short of the readies ,wanted her to give him some money; a depraved person ,a girl who used to work for her ,actually her lover and her victim. 2) A jeweler is arrested by two cops in uniform but it seems to be a miscarriage of justice ;it's all the more strange since shortly after we see the two policemen stealing jewels from the shop..