So much of writer-director John Lee Hancock’s psychological cop thriller, “The Little Things,” seems recognizable and pre-ordained on the surface. The drama offers the trope of a grizzled veteran cop (Denzel Washington) conflicting with a talented younger detective who’s made the grade (Rami Malek), the way they clash, break balls, their various obsessions, a haunted past, and a quirky, alleged serial killer (Jared Leto), not afraid to tease and taunt the police. But as the slow-burning, seemingly conventional picture unfolds and develops, it actually takes the viewer by surprise. Especially in its upending, pivoting-away-from-crime norms, morally ambiguous ending, Hancock’s picture reveals itself to have much more on its mind than expected, and becomes a thoughtful meditation on the rigors of police work and the psychic toll that it takes on the soul.