See How They Fall - Jacques Audiard

Simon is a sales representative about fifty. When Mickey, his cop friend, is being shot, he leaves everything to find the murderers. Two years before, Marx, an old gambler, met Frederic, a young man that does not look very smart and started to follow him everywhere (as a puppy) and changed his name to Johnny to please Marx. Of course, Simon's story is related with Marx and Johnny's one. But the thriller is only a pretext for a psychological description of the three main characters.