The film begins with Bailey, narrated by Josh Gad, sharing his journey through life as a dog. He starts as a newborn puppy seeking milk from his mother, eventually rummaging through garbage with his siblings. Sadly, two men capture him, placing him in a vehicle destined for the city pound, and it becomes clear the vehicle is outdated. It is hinted that he faces an untimely fate there.
Bailey comes to in a cage, shocked to remember his past life. Set in the 1960s, he discovers he's in a pet store filled with various breeds of dogs. The handler presents him to a client as a 'Red Retriever,' but the customer prefers smaller dogs. After escaping through an unsecured part of the fence, he finds himself in a pickup truck, where two men plan to sell him for a quick buck. When they go inside a building, Bailey is left in a hot truck, and just as he's about to give up hope, a kind boy named Ethan (played by Bryce Gheisar) and his mother rescue him. They nurse him back to health, and soon, Ethan's father, who struggles with alcoholism, is introduced into the picture.
Ethan's family decides to keep Bailey, attaching a tag with his name on one side and Ethan Montgomery on the other, a detail that becomes significant later on. The bond between Bailey and Ethan grows as they navigate life together, amidst the chaos of the father's drinking problem. Bailey brings joy to the household, having fun with the family, learning 'dog lessons,' and cherishing every moment spent with Ethan, whom he fondly refers to as 'Boss Dog.'
As the years pass, the story fast-forwards to a teenage Ethan (now played by K.J. Apa), who excels as the star quarterback in high school. Unfortunately, his relationship with his father deteriorates further, leading to domestic conflict. Nonetheless, Bailey continues to support Ethan through these trials, even helping him connect with a girl named Hannah (portrayed by Britt Robertson), igniting young love. Tensions rise, and after an unfortunate fire instigated by Ethan’s rival, everything culminates in tragedy when Ethan ends up seriously injured.
Bailey finds himself left behind as Ethan moves to learn farm life and reluctantly leaves the cherished dog behind. The separation weighs heavily on Bailey's heart, representing a loss that feels insurmountable. The narrative takes a shift as Bailey reincarnates into Ellie, a female German Shepherd and police canine in training. Initially struggling with her new life's challenges, Ellie eventually proves her worth by rescuing a kidnapped girl, earning the love and trust of her handler, Carlos (played by John Ortiz).
The story continues as Bailey transforms once more, this time into Toby, a Corgi adopted by Maya (portrayed by Kirby Howell-Baptiste). His adventures unfold in a college setting, featuring comedic mishaps surrounding his newfound life, love interests, and the challenges of growing up. Toby’s life takes a turn when he falls into depression due to the loss of his beloved friend, Roxie.
Finally, the narrative leads to Toby's next reincarnation as Buddy, a St. Bernard mix. Initially mistreated and abandoned, Buddy eventually finds his way back to Ethan’s home. However, Ethan, now an older man (played by Dennis Quaid), struggles with loneliness. A reunion leads to revelations as Buddy, now linked to memories of Bailey, rekindles the bond they once shared. The heartfelt conclusion sees Ethan and his childhood love, Hannah, reconnecting, ultimately leading to their marriage.
In a beautiful callback to the past, Ethan creates a new tag for Buddy, encapsulating the essence of Bailey's journey, emphasizing that a dog's purpose is to spread joy and help others embrace that happiness. The film's final moments resonate with a universal truth, reminding audiences of the bonds shared between humans and their loyal companions.
