In the Valley of Elah (2007)

On his first weekend back after serving in Iraq, Mike Deerfield goes missing and is reported AWOL. When Hank Deerfield, a former military MP and his wife Joan get the phone call with the disturbing news, Hank sets out to search for their son. Emily Sanders, a police detective in the jurisdiction where Mike was last seen, reluctantly helps him in his search. As the evidence grows, her missing person's case begins to look more and more like foul play, and soon Sanders finds herself in a fight with the military brass as she and Hank struggle to keep control of the investigation. But when the truth about Mike's time in Iraq finally begins to emerge, Hank's entire world is challenged and he's forced to reevaluate long-held beliefs to solve the mystery behind his son's disappearance.