The Valley of Elah is the legendary spot between two mountains where, according to 1 Samuel, young David slew the mighty Philistine warrior Goliath. The site is an appropriate allusion for writer-director Paul Haggis’s movie about the American experience in Iraq. In the Valley of Elah posits that the U.S. may be the military Goliath brought down by hit-and-run insurgents.

The story, based in part on a chilling Playboy article by Mark Boal, focuses on American soldiers who have just returned from Iraq to a base in New Mexico. One of them, Mike Deerfield (Jonathan Tucker), is reported AWOL within days of his return. When news of Mike’s disappearance reaches his tough-as-nails father, the ex–military MP Hank Deerfield (Tommy Lee Jones), the old man decides to leave his business to find his boy. So begins a story that is part Parable of the Prodigal Son and part John Ford’s The Searchers.

Hank’s eyes are opened as he discovers what Mike and his fellow soldiers went through in Iraq. His investigation leads him to a series of bureaucratic barriers, both military and procedural, as the missing-persons case turns into a murder investigation.

Finding little assistance from his once-trusted allies in the military, Hank turns to the police. At first, he is rebuffed as an obsessed old man. Then he makes a connection with rookie detective Emily Sanders (Charlize Theron), a single mother who is impressed by Hank’s intensity and intimidated by his superior sleuthing. Together they dig for clues, rush down dark alleys and encounter dead ends. Only when hope is almost gone does Hank learn that the truth has been staring him in the face all along.

What makes the film memorable are the moments when Hank and Emily are on the job. Hank gets to know her timid son, David, who has never heard the biblical tale of his famous namesake. When Hank relates the story to him, it dawns on the viewer that Hank probably told the same story to Mike as a boy, and that Mike’s willingness to face down his own fears may have led to his death.

Highlights of the film include the performance of Susan Sarandon as Hank’s wife, Joan, who is left behind to worry, just as she has worried about her military husband and sons for decades. She is not a passive observer, however; in a scene that rings painfully true, she lashes out at Hank for his warrior mentality that led to the destruction of their family.

Also impressive are the performances of the young actors—including two men who served in Iraq—who portray Mike’s battle mates and friends. The scenes in which they try to articulate what it was like in Iraq end in confusion and tears. This emotional chaos is reinforced by the random images of battle that are on Mike’s cell phone—all pieces of the puzzle that Hank is trying to put together.

Jones is so powerful in the role of Hank Deerfield that I wanted to believe in the film’s concluding image. But that political coda is the weak spot in a masterful film, which didn’t need to slap us across the face to wake us up.