Retired army sergeant Hank Deerfield (Jones) has already lost one son to war when he gets a call telling him that his youngest Mike (Jonathan Tucker) has returned safely from Iraq, but has gone AWOL. Finding that completely out of character, he kisses wife Joan (Sarandon) goodbye and heads for the boy's base to do some investigating. But he has barely gotten started when Mike's stabbed, burned, and dismembered body is discovered strewn across the desert outside of town. The local cops palm the case off on the army; the army shows little interest in pursuing it, leaving the grieving father to soldier on alone until newbie detective Emily Sanders (Theron), with something to prove to the men in her department, agrees to take the case.

A true story by Mark Boal that appeared in Playboy serves as the springboard for this tale. Haggis adds in another real-life incident and then fictionalizes the whole thing. Jones is so good as the grieving, yet determined father that the drama almost works, but ultimately if falls to pieces. The filmmaker wants to say something about the war and its costs, but his message is heavy-handed, overblown, and way too simple. Deerfield thinks that he knows his son, but as he watches broken images from cell phone movies Mike shot in Iraq, takes in police theories that his boy might have been involved with drug trafficking, learns about Mike's escapades in a strip club, and hears tales from his buddies of how he behaved in Iraq, the picture that emerges is that of a stranger. As Deerfield gets to know his son's friends, they, too, morph before his very eyes from upstanding young men into merciless fighting machines, unsure or unable to turn off now that their own part in the killing is done.

Adding to Haggis' thesis is a subplot in which a battle-scarred veteran's wife reaches out to Sanders for protection from the husband she fears, only to be turned away since he hasn't hurt her yet. Haggis is guilty of murder himself, for the way he hammers every point home. Subtlety is not among his strengths, which he proves again with yet another subplot as Sanders has to fight for respect from her male colleagues, all enthusiastic practitioners of sexual harassment. In the world of In the Valley of Elah, war veterans or not, unless they possess Deerfield's wisdom or die like Mike, men are just beasts.

Near the beginning of the film, Deerfield spots a flag mistakenly hung upside down, the signal of distress. It is the most elegant image in the movie, foreshadowing what Deerfield is about to experience. It is a graceful moment in an otherwise uninspired, sometimes downright insipid drama. Jones' terrific performance is the only real reason to visit this Valley, but that might not be reason enough.