The title is a colloquialism for being injured in an explosion, as in "they sent him to the hurt locker", or for "a place of ultimate pain". It dates back to the Vietnam War, where it was one of several phrases meaning "in trouble or at a disadvantage; in bad shape."
The Hurt Locker opens with a quotation from War Is a Force That Gives Us Meaning, a best-selling 2002 book by New York Times war correspondent and journalist Chris Hedges: "The rush of battle is a potent and often lethal addiction, for war is a drug."
During the early stages of the post-invasion period in Iraq in 2004, Sergeant First Class William James, a battle-tested veteran, becomes the team leader of a U.S. Army Explosive Ordnance Disposal (EOD) unit, replacing Staff Sergeant Thompson, who was killed by a radio-controlled 155mm improvised explosive device (IED) in Baghdad. He joins Sergeant J.T. Sanborn and Specialist Owen Eldridge, whose jobs are to communicate with their team leader via radio inside his bombsuit, and provide him with rifle cover while he examines IEDs. During their missions of disarming IEDs and engaging insurgents together, James's unorthodox methods lead Sanborn and Eldridge to consider him reckless. Tensions mount between James and the other two team members. During a raid on a warehouse, James discovers the dead body of a young boy who has been surgically implanted with an unexploded bomb. James believes it to be "Beckham", a young Iraqi merchant he had previously befriended.
Later, James orders his team to pursue two insurgents responsible for a recent explosion. Sanborn protests that the task should be left to an infantry platoon, but James overrules him. During the operation, Eldridge is accidentally shot in the leg. The next morning, James is approached by Beckham. The young boy tries to converse with James, who walks by without saying a word. Being airlifted for surgery, Eldridge angrily blames James for his injury.
After failing in a mission to remove and disarm a time-bomb strapped to an Iraqi civilian's chest, Sanborn becomes emotional and confesses to James that he can no longer cope with the pressure of being in EOD, and he looks forward to finally leaving Iraq and starting a family. James returns home to his wife and child and is shown quietly performing the routine tasks of suburban civilian life. One night James confesses to his infant son that there is only one thing that he knows he loves. He is next seen back in Iraq, ready to serve another 365 days as an EOD team member with Delta Company.