The title character in this moody French policier is not little but young and inexperienced — he’s a police-academy standout who earns a job on the Parisian homicide squad. Newly assigned top cop Commandant Caroline Vaudieu (Nathalie Baye) takes a more than professional interest in him, noting that Lieutenant Derouère (Jalil Lespert) — handsome, book-smart, street-dumb — is about the same age her own son would have been had he not died at age seven, a loss that ended her marriage and fueled a two-decade struggle with alcohol. It’s left to the mouthy male crew to school the hapless young rube, and he’s an eager student of the mordant Lieutenant Morbé (the film’s director, Xavier Beauvois), who tells him, “You’re paid to lock up Arabs and blacks — if my pet lizard freaks you out, join Narcotics.” Invoking Jean-Pierre Melville, Beauvois emphasizes emotions over procedures, and so elements of a particular crime remind Vaudieu how common it is to do justice, and how difficult it is to do right.