The provocatively-titled "Gone Baby Gone" peels itself one layer at a time, revealing unpredicted and mesmeric sides to a story that could never be guessed from the initial setup. Based on the novel by Dennis Lehane and auspiciously adapted for the screen by Ben Affleck (also making his directorial debut) and Aaron Stockard, the film begins as a relatively conventional kidnapping drama but ultimately turns out to be so much more than that. As the investigative procedural gets underway, potential suspects are questioned, and the safety of the victim is put into question, an in-his-element Affleck veers the narrative in sharply diverse directions. The twists, if one wants to call them that, are neither obligatory nor cheaply contrived for the sole purpose of jerking around the audience. Instead, they happen loosely and surprisingly, as real life does, and significantly supplement a motion picture that has a lot to say about human loss, parenting, child neglect, and ethical dilemmas involving whether what is lawful is always the right decision.

When 4-year-old Amanda McCready (Madeline O'Brien) goes missing from a lower-class South Boston neighborhood, young self-employed investigator Patrick Kenzie (Casey Affleck) and girlfriend/associate Angie Gennaro (Michelle Monaghan) are hired by the child's worried aunt (Amy Madigan) and uncle (Titus Welliver) to look into the disappearance. With Amanda's drug-addled mother Helene (Amy Ryan) being of little help, Patrick and Angie work concurrently with law enforcement—namely, Captain Jack Doyle (Morgan Freeman) and Detective Remy Bressant (Ed Harris)—in the hopes of either bringing Amanda home safely or bringing her captor/murderer to justice. As details involving Amanda's unsavory upbringing are brought to light, Patrick and Angie are left to question the extent of what is waiting for her if she is found alive.

Ben Affleck, an Oscar-winning screenwriter for 1997's "Good Will Hunting" and an underrated actor last seen in 2006's "Hollywoodland," can safely add filmmaker to his list of talents. "Gone Baby Gone" doesn't look or feel like the work of a novice director, but of a veteran artist who intimately understands the medium and knows how to effectively rattle the senses of viewers without broadly manipulating them. Superficially, the movie's plot reminds of 2006's severely overwrought "Freedomland" and the mellow tone and gritty setting recall 2003's exploitatively self-serious "Mystic River" (coincidentally also based on a novel by Lehane). "Gone Baby Gone" is superior to both of those efforts, staying low-key and naturalistic even as multiple revelations in the second hour force one to reassess certain characters' beliefs and viewpoints while intriguingly depicting their tough moral quandaries. That director Affleck does not indefinitely provide answers as much as he leaves the debates open to personal interpretation is a smart choice that further lifts the film well above a standard police investigation flick.

Casey Affleck (Ben's little brother) gets the lead role, but this is not a case of nepotism winning out over proper casting. In what is turning out to be Casey's year to prove his mettle as an actor to be reckoned with—his Oscar-worthy work in "The Assassination of Jesse James by the Coward Robert Ford" also deserves notice—the younger Affleck is commanding yet laid-back as investigator Patrick Kenzie, a 31-year-old who looks much younger than his age and isn't quite prepared for the lengths he is about to go in the name of his job and his conscience.

As girlfriend and work partner Angie Gennaro, Michelle Monaghan (2007's "The Heartbreak Kid") gives the picture an empathetic maternal edge lacking with Amanda's actual mother, but is otherwise saddled with a character not as fleshed out as she could have been. Monaghan is overshadowed by Affleck, whom she shares all her scenes with, and is more or less left to react to the things around her. If the film hits a snag in its framework—and it's a minor one—it is the fact that Patrick and Angie are as young and wet-behind-the-ears as they are. As investigators, they are good at what they do, but by not having children of their own or clearly having the level of life experiences under their belt as those around them, their heightened emotions and actions pertaining to the kidnapped Amanda are not always wholeheartedly plausible.

Supporting work is superlative. Ed Harris (2005's "A History of Violence") is intense as Detective Remy Bressant, hinting at the anger and willingness to commit violence hiding behind his respected badge. Morgan Freeman (2007's "Feast of Love") is wise and sad-eyed as Captain Jack Doyle, a John Walsh-like figure who has dedicated his life to finding missing persons after the tragic murder of his own 12-year-old daughter. As Helene McCready, mother of the missing Amanda, Amy Ryan (2005's "Capote") delivers a breakthrough performance, essaying a pathetic, self-absorbed creature who somehow shows her humanity even when said humanity is of the unflattering variety. Ryan runs away with her part to the point where she is head and shoulders the most memorable among an ensemble with more screen time than she has.

Transcending its landscape even as it very specifically has been filmed on-location in Boston, "Gone Baby Gone" captures the communal flavor and darker underbelly of that New England city while spinning an uncompromising tale that will prove enthralling and relatable for adult audiences. The true themes hiding underneath the basic kidnapping conflict are where the film earns its power, but they must remain purposefully vague in this review so as to not give anything away. Suffice it to say, the movie does not jump the rails as further plot turns are uncovered, but strengthens itself through them. The final scene, perfectly scripted and performed, sends "Gone Baby Gone" out on a high note. As for the very last line of spoken dialogue, it is as staggeringly telling as it is unremittingly haunting.