The story begins in the gritty, working class Boston neighborhood of Dorchester where 4 year old Amanda McCready has gone missing without a trace. The police have failed to turn up even the narrowest of leads, so Amanda’s desperate Aunt and Uncle plead with local private investigators Patrick Kenzie (Casey Affleck) and Angie Genarro (Michelle Monaghan) to take the case. Though they’re wary to jump in, Patrick and Angie know the neighborhood and the truth about Amanda’s drug-addicted mother Helene (Amy Ryan).

As they investigate her story, they find themselves on a trail that winds into the dark heart of Dorchester and through a chain of drug-dealers, ex-cons and child abusers, but brings them no closer to Amanda. In the glare of the media spotlight, they join forces with a relentless detective Remy Bressant (Ed Harris) and police captain Jack Doyle (Morgan Freeman). As Patrick examines the clues, he finds himself lured into an ever-intensifying web of lies and inexplicable violence until he comes face to face with a complicated moral dilemma with no easy answers.