Plot
In the 1950s, a feral puppy wonders about life's true purpose. Weeks later, he is caught by dog catchers, taken to the pound, and euthanized.
The dog is reborn as a Red Retriever in 1961. Leaving his cage at a puppy mill, he is taken by two garbage men who plan to sell him. Left locked inside their pick-up truck, he begins to die of heatstroke, but is rescued by an eight-year-old boy named Ethan Montgomery and his mother Elizabeth. They break the truck's window and bring him home, naming him Bailey. After his father Jim reluctantly allows him to keep the dog, Ethan bonds with Bailey quickly, especially over the summer at the farm of Ethan's grandparents Fran and Bill, and Bailey decides Ethan alone is his purpose.
Years pass, and after several attempts at advancing in his job fail, Jim has become an alcoholic. In 1969, Ethan meets Hannah at a fair with Bailey, and they soon begin dating. They spend their summer together through senior year. They plan to go to the same college, Ethan getting a football scholarship and Hannah with an academic one. At home one night, a drunken Jim becomes abusive towards Ethan and Elizabeth. Ethan orders him to leave and never return, which he does.
Later in 1971 at a football game watched by scouts, Ethan is offered a full scholarship to Michigan State. That night, his vindictive classmate Todd throws a lit firecracker into Ethan's house, causing a house fire. Bailey alerts Ethan, who saves his mother out through an upstairs window. Ethan lowers her, then Bailey. However, he loses his rope and has to jump, fracturing his leg. Bailey attacks Todd, who is arrested by the police when firecrackers fall out of his pocket. With his athletic scholarship canceled, Ethan has to go to an agricultural school, where he will learn to take over the farm. Depressed, Ethan breaks up with Hannah before leaving for college, while Bailey stays with Fran and Bill. Bailey ages and Ethan comes to say goodbye as he dies.
Bailey is reborn as a female German Shepherd puppy, growing into a police dog named Ellie, in the late 1970s/early 1980s, while fully retaining memories of her past lives. Ellie is partnered with officer Carlos Ruiz, who has recently split up with his partner of the Chicago Police Department and works hard at "seeking" and "finding", now seeing the job as life's purpose. They form a close bond, ending after Ellie saves a girl, kidnapped by her mother's ex-boyfriend, from drowning and is then fatally shot by the kidnapper while protecting Carlos.
Reborn in the mid-1980s as a male Corgi, Bailey is adopted by Atlanta college student Maya, who names him Tino. Lonely, he tries to find her happiness. She meets Al, a classmate, after Tino falls for Al's dog, a female Landseer named Roxy. They marry, having three children. Tino is heartbroken when one day Roxy does not return from the vet. As a now elderly Tino dies, he thanks Maya for giving him one of his best lives.
Bailey reincarnates again, this time as a St. Bernard/Australian Shepherd mix puppy in 2014. At first adopted by Wendi, he is named Waffles. Wendi's husband neglects him, refuses to let her keep him inside, and after several years, abandons him. Waffles searches for a new life, gradually returning to where he spent summers as Bailey. He reunites with his old master Ethan, now in his 60s, living on his grandparents' old farm. Not recognizing him, Ethan takes him to the local animal shelter, but later reclaims him, naming him Buddy.
Finally sensing that he has finally found his true purpose, he reunites Ethan with a widowed Hannah, and they get married. Buddy shows Ethan that he is his beloved childhood dog, by performing tricks and responding to phrases that were known only to the two of them many years back, such as "boss dog". Ethan finds Bailey's collar, now old and rusty, and places it back on Bailey's neck, and they resume playing exactly the way they did years ago. Bailey narrates that life is about having fun, saving others, finding someone to be with, not getting upset over the past or the future, and living for today.
