Purple Heart is a young adult novel by National Book Award Finalist Patricia McCormick, first published in 2009. The novel begins as 18-year-old Army Private Matt Duffy wakes up in a medical ward in Iraq and discovers he has a traumatic brain injury, or TBI. Matt doesn’t remember how he ended up in the hospital and recalls only the image of an Iraqi boy in an alley, a boy who is lifted off the ground in a “sudden, silent flash of light” and floats “high up into the crayon-blue sky” (4).

For the first few days of his hospital stay, Matt drifts in and out of consciousness and has trouble moving far from his bed. He is awarded a Purple Heart “for wounds sustained in combat” (5) and talks to an Army chaplain, Father Brennan, whom Matt feels a connection to because of his own Catholic upbringing. Matt’s doctor, Dr. Kwong, tells him he may have trouble with remembering and processing information as well as regulating his emotions. Throughout his hospital stay, Matt has difficulty recalling simple words such as “raincoat” (41), and he finds himself frustrated.

Matt’s squad mate Justin visits and tells Matt how he ended up in the hospital: in a Humvee, Matt and Justin pursued a taxi that had burst through the Army barricade, and they ended up in an alley, separated from the rest of their squad. Now on foot, Justin shot a “haji bastard” (21) in the alley, and Matt was hit by an RPG—rocket-propelled grenade. As squad mates, Justin and Matt are “inseparable” (36), and Justin risked his own safety to drag Matt out of the alley while under enemy fire.

Matt is allowed a phone call to tell his family what happened. He has a single mom he feels the need to protect, as Matt downplays his injuries during the call. Matt has one sister, high-schooler Lizzy, and he joined the Army at least partly to provide her with college money.

Matt watches Iraqi kids playing outside the hospital and thinks about Ali, the 10-year-old orphan he befriended when his squad was ordered to “establish contacts” (28)with the Iraqis. Ali stole Matt’s sunglasses but later returned them; he is a skilled soccer player and artist. Matt is disturbed to realize Ali is the boy he remembers seeing before being hit by the RPG—the boy in the alley, engulfed in a "flash of light" and flying into the sky.

Matt has a series of meetings with Officer Meaghan Finnerty, whose job is to evaluate Matt’s brain injury and determine whether he can rejoin his squad. Matt is desperate to get back to his unit, whom he considers family, but he can’t hide his difficulties remembering simple words or what happened just before he was injured.

Matt receives a letter from his girlfriend, Caroline, and while he used to be comforted by descriptions of her ordinary, safe high-school life, now her focus on trivial matters like a bio test just upsets him. Still desperate to remember what happened in the alley, Matt keeps track of his memories in a notebook given by him to a fellow patient, Francis. Hearing the “pop-pop-pop of an AK-47” (66) jars Matt into remembering something else: he now knows that the boy in the alley was shot. He tells Meaghan that he thinks the boy was Ali—and that he believes he killed him.

Francis accidentally killed Matt's squad leader in an incident of friendly fire. After an exchange with Francis, Matt also learns that the jail term for killing an Iraqi citizen is 20 years. Matt is even more nervous when he’s escorted to Lieutenant Colonel Fuchs’s office to be questioned about the incident. At the meeting, also attended by Lieutenant Brody, Fuchs explains that the Iraqis are claiming a 10-year-old civilian—Ali—was killed “intentionally” (100), but that there’s “a lot of confusion” (102) in Iraq about who is and isn’t an enemy.

Back on the medical ward, Matt learns that Francis is being sent away because of his pill addiction. He visits Meaghan again, and she tells him his mind may have buried the memory of shooting Ali. Then Matt tries to confess what he’s done to Father Brennan, but he’s unable to get the words out.

Matt meets with Lieutenant Brody, but Brody doesn’t ask Matt a single question—instead he tells Matt that because of his brain injury, his memory is unreliable, and Ali’s death will be written up as “collateral damage” (121). The next morning both Meaghan and Dr. Kwong clear Matt to return to his unit; before leaving the medical ward, Matt gives his Purple Heart to Father Brennan, who says he’ll hold on to it until Matt is ready.

Matt returns to his squad and is relieved to be back with his friends, although Justin seems to be avoiding him. Matt’s squad leader, Sergeant McNally, pairs Matt with the squad’s only female member, Charlene, because he wants Matt to “take it easy” (146). There’s a cease-fire, so patrols are more relaxed than usual, but Matt still has a hard time keeping up and is emotionally on edge. When the squad patrols near the alley where he was injured, he sneaks away to examine the scene—and he realizes that Ali was standing across from the window where Justin was positioned. Because of the angle at which Ali’s body fell, he must have been shot from that window—meaning Justin, not Matt, killed Ali.

Justin continues to avoid Matt, unwilling to discuss what happened, while at the same time Matt is growing closer to Charlene. He thought she had always been standoffish, but now Matt notices a “little hint of warmth in her eyes” (148). While the squad is patrolling a market, a suicide bomber sets off an explosion, killing Charlene as well as another of Matt’s friends, Wolf. Justin protects Matt while he’s carrying Charlene’s body, and Justin’s leg is injured. Before Justin is evacuated, he tells Matt that he shot Ali, because Ali was a “spotter” (185) relaying Matt’s location to the insurgents.

Matt replays the image of Ali’s death one more time and realizes the boy was wearing shoes with soccer cleats—something he could have only gotten from the insurgents. Matt reflects that by befriending Ali, he actually caused the boy’s death and endangered his own squad. If Matt and Ali weren’t so close, Ali wouldn’t have been valuable to the enemy.

After preparing for Charlene and Wolf’s memorial service, Matt accompanies Sergeant McNally on a supply run, where he watches a group of kids playing. One of the children kicks a soccer ball into the street and they all scream for Matt to kick it back, but he freezes. Then a little girl gives him a thumbs-up—she seems to see him not as just an American soldier—and the gesture jolts Matt back to life. The book ends as Matt kicks the ball back toward the children and watches it “sail[ing] into the crayon-blue sky” (199)—the same “crayon-blue sky” into which Ali floated away at the opening of the novel.