So, why the heck doesn't it work?
The Little Things starts off promisingly enough, with a tense, unnerving scene of a young woman being pursued by a mysterious driver at night on a highway near Bakersfield. We then cut to Joe Deacon (Washington), a lowly sheriff's deputy in Kern County, California, as he returns to his old haunt of Los Angeles and unofficially joins the investigation into a rash of serial killings that bear some resemblance to murders that occurred when he was a homicide detective in L.A. Deacon is haunted, it seems, both by the women whose deaths he couldn't solve — he talks to corpses and, at night, imagines the dead staring back at him — and by the unspecified cloud under which he left the department. His former partners and colleagues in the L.A. Sheriff's Department view him with a combination of standoffishness and outright disdain.
But not Jim Baxter (Rami Malek), the young hotshot homicide detective in charge of the case, who is fascinated by Deacon and asks for his help in solving these crimes. For all his cocksure bravado, Baxter seems untainted by the cynicism and mordancy of the weary veterans around him. He still believes that as investigators they are working for the dead victims, and avoids his fellow cops' chummy, banter-y gallows humor. Deacon doesn't share Baxter's earnestness, not any more, but he does share his clarity of purpose. ("Things probably changed a lot since you left." "Still gotta catch "em, right?" "Yeah." "Not that much has changed, then.") He teaches Baxter to take note of the "little things," the overlooked details of a crime scene or a perpetrator's psychology that could give them clues as to who he might be.
On paper, it sounds great. As a genre piece, however, The Little Things is somewhat undermined by its inability — or perhaps unwillingness — to clarify the parameters of the case, to establish who or what our heroes are looking for. That's not a fatal flaw, and it could have been an asset: The film seems more interested in the psychological toll of police work, of the debilitating drudgery of failure; it wants to be more character study than procedural. But it half-asses that, alas. The script plays coy with the skeletons in Deacon's closet, waiting until the end to reveal their exact nature, which is a cheat because almost every other character knows what those skeletons are. (Baxter doesn't, but the film isn't from Baxter's point of view — it's mostly from Deacon's.)
This screenwriter's ploy winds up damaging the performances. Because we don't know the real source of Deacon's torment, his brooding comes off as vague and generic, and there's little Washington can do with the part other than, well, look tormented. Malek, meanwhile, never seems comfortable in the role of the idealistic detective; it feels like he's playing an idea, rather than a person. Furthermore, beyond the initial setup of their relationship, the interactions between Deacon and Baxter don't really develop in any meaningful way, save for a sudden turn right at the end. Maybe in the hands of a director with a better control of mood, a firmer focus on characters, and a sharper understanding of how to play with pulp iconography — say, Eastwood, and in particular '90s Eastwood — it might have worked.