The idea behind a good police procedural is that if you follow a case step by step, getting all the minute details right, thematic or character-based revelations will arise naturally as a result. After all, how detectives go about their work can be telling, and their encounters in the field can speak volumes about social ills. Xavier Beauvois' Le Petit Lieutenant goes about its business with an unfussy, workmanlike dignity that scrapes dangerously close to tedium at times, especially in the first half, when it parses out information like drops from a leaky faucet. But all that steady accumulation of detail, enhanced by a pair of affecting lead performances, pays off later, as tragedy strikes and the stakes are made bracingly clear. If this were staged as run-of-the-mill melodrama, it would be over the top.
Fresh from the Academy, eager young policeman Jalil Lespert requests assignment in a Paris detective bureau and unexpectedly gets it, but the surprise doesn't sit well with his wife (Bérangère Allaux), who refuses to leave their provincial home. This leads the lonely Lespert to rent space in the city and immerse himself in his work, but first he has the sensitive task of acclimating to a staff of varying ethnicities and sensibilities. The division's new chief inspector is Nathalie Baye, a recovering alcoholic who hit the bottle hard after meningitis took her 7-year-old son. Over time, the self-effacing Lespert reignites Baye's motherly instincts, and the two develop a special relationship as they look into the murder of a homeless Pole.
Le Petit Lieutenant spends too much time laying the groundwork for a story that could be told more succinctly, but Beauvois works hard to establish office chemistry and orient Lespert to his new surroundings. The ins and outs of the murder case also aren't terribly compelling or memorable, but they provide enough incident to test the investigators' resolve and send them reeling in the closing minutes. In the end, the film belongs to Baye, a veteran French actress who handles the part with toughness and vulnerability without overselling either facet of her character. It's just the sort of minor triumph that Beauvois seems content to achieve.