"Familiar" is usually not a favorable adjective in a movie review, but in the case of "The Little Things," it's not a criticism.
The thriller is familiar because it's the latest in a long line of Denzel Washington-mentors-a-younger-cop movies, and because its serial killer tropes have popped up many times in the post-"Seven" era: police flashlights piercing a dark room filled with forensic evidence, ironic R&B music from the '60s, neon-stained streets, a murder board packed with photos and clues.
None of these things will dazzle moviegoers with their originality, but they succeed at establishing a tense mood.
They also work because Washington, like Tom Hanks or Jessica Lange, is one of those actors whose connection to the audience is such that we'll follow him pretty much anywhere. I wish he'd test that more often (a comedy, maybe?) but he's adept at varying the specifics of the people he plays, all of whom have solid names like his moniker in "Little Things": Joe Deacon.
He's a decent guy (practically the first thing we see him do is scratch a mutt's back) with a dark secret (there's talk of how his obsession with a case got him exiled from Los Angeles) and a willingness to overlook his mentee's arrogance (the first thing Rami Malek's Sgt. Jim Baxter does is try to get Joe's car towed) — if it'll help solve their case.
Washington makes Joe authoritative, intelligent and vaguely haunted, all of which tracks — and positions him opposite the callow Baxter, who's written to be like a dog with a bone and who becomes even less nuanced in Malek's half-note performance.
They're trying to solve the grisly murders of young women in L.A., which a colleague compares to the recently solved Night Stalker killings (as evidenced by all the boxy cars, "Little Things" is set in the '90s).
There's intriguing character stuff here: Deacon is skilled at his work but not his life, talks to corpses in an effort to understand the killer and has stopped believing in God because of all the terrible stuff he's seen.