Gloomy and without concessions, this film definitely won't make you happier after watching it, but it's so well made you will probably get into the plot, even with the slow pace and naif styling common in 50's French cinema.
Of course Gabin is a "good guy", tired, tough, but ultimately fair. Even if he's constantly showing he's tired of the job, being badly paid, quite impatient, etc. Needlessly, he steals the movie. The young stars don't disappoint. Maybe Francis is a bit too slick for the age, being sort of a natural leader who never misses a cue. Alain's ingenuity is believable, and that's quite a feat for a child actor. Sylvette is also right on track as the "beautiful working class bitter heroine". The prostitute step mum's treatment is also an interesting character, given she's never given moral lessons or shown "what happens to those people", unlike other films of the epoch. Finally, as usual, no "accompanying music" and a "minimalist" in the sense of austere décor aid for this film's oppressive feeling you get while watching it.
IMDb's pro reviewer "Dumnteil" is accurate as usual when comparing it favourably with the way more famous "400 coups". Enjoy!