Plot
Jackson Briggs, a former U.S. Army Ranger suffering from PTSD, tries to apply for a rotation position in Pakistan, but is deemed unfit for service due to a brain injury. He is notified that his friend and former partner, Riley Rodriguez, was killed in a car crash the night before. The morning after attending a memorial service at a local bar, Briggs is called in to Fort Lewis on a special assignment to escort Riley's military dog, Lulu, a female Belgian Malinois with a history of aggressive behavior, to attend his funeral in Nogales, Arizona, after which he is to bring her to White Sands, where she will be euthanized. Initially hesitant, Briggs agrees when his former company commander, Captain Jones, promises to recommend him for the rotation position.
On the road, when Briggs stops at a shooting range, Lulu is disturbed by the sound of gunfire due to her military experiences. She breaks out of her cage, and destroys the passenger seat of his 1984 Ford Bronco. Frustrated, Briggs gives her Benadryl hidden in a hot dog, causing Lulu to fall asleep. In Portland, Oregon, Briggs tries to hit on various women at a bar, but most are repelled by his brash personality. Outside, Lulu draws the attention of two friends, Bella and Zoe, who invite Briggs back to their house. While he is inside, Lulu's barking alerts a neighbor. Believing her to be the victim of abuse, the neighbor smashes the rear windshield, but she promptly attacks him. Briggs runs outside and pulls them apart, but Bella and Zoe are disturbed by the display and lock Briggs outside.
The next morning, while on the Pacific Coast Highway, Lulu climbs out the broken rear windshield, forcing Briggs to pull over and chase her through a nearby forest. They stumble across a marijuana farm, where Briggs is tranquilized by the farm's owner, Gus. He wakes up tied to a chair, but is able to escape. Lulu is being treated by Gus's wife, Tamara, as she has injured her paw. Briggs and Gus reconcile by looking through Lulu's "I Love Me" book, which contains photos from her service during the War in Afghanistan.
In San Francisco, Briggs cons his way into a free room at a luxury hotel by pretending to be a blind veteran, with Lulu as his seeing-eye dog. He tries to leave for the evening, but Lulu barks until Briggs relents and takes her with him. In the lobby, Lulu attacks a Middle Eastern man wearing a thawb, Dr. Al-Farid, due to her military training. Briggs is arrested under suspicion of committing a hate crime. During a lineup at the station, Briggs apologizes to Al-Farid, who agrees not to press charges on the condition that Briggs seek professional help. While retrieving Lulu from animal control, an employee explains that Lulu's heavy panting is an expression of anxiety. In Los Angeles, Briggs tries to visit his 3-year-old daughter, Sam, but his wife, Niki, does not allow it. Briggs visits Noah, a former Army Ranger who adopted and rehabilitated Lulu's brother, Nuke. Noah teaches Briggs to bond with Lulu in terms she understands, allowing him to form a deeper connection with her.
The Bronco breaks down during a thunderstorm, forcing Briggs and Lulu to shelter in an abandoned barn. The next morning, Briggs and Lulu hitchhike to Nogales in time for the funeral, where Briggs reassures her during the traditional rifle salute. He calls Jones and tells him that he is hopeful that Lulu will not have to be put down due to her improvements over the trip, but Jones tells him that the decision is not up to them. Briggs drives into the desert and encourages Lulu to run away, but she refuses. While staying the night in a motel, Briggs has a panic attack and seizure, but is comforted by Lulu.
In the morning, Briggs hands Lulu off at White Sands, but cannot bring himself to drive away when he sees her distress at him leaving. He returns and takes Lulu back, driving away with her. Months later, after successfully adopting Lulu, Briggs writes a letter thanking her for saving his life and making him a better man. Briggs is shown to have reconciled with Niki and Sam, as well as begun connecting with Noah and other retired veterans.
