The main character Toby is in his first life and is taken to the yard where he learn what it is like to live in a pack. When Toby and his brother got in a fight with Spike where Toby's leg is snapped. People take Toby away and kill him. This is his first life.
The young dog wants to find out the meaning of a dog or a dog's purpose. He wants to find out why dogs are here.
I am starving and thirsty!
He is reborn as Bailey and meets his new owner Ethan. He lives with Ethan. Todd and Ethan got into a fight. That night, Todd sets Ethan's house on fire and Ethan jumps out of a window and breaks his leg. Bailey is brought down to the Farm where Grandpa and Grandma live and he stays with them. A lot of time passed and Bailey dies of old age.
I have fulfilled my purpose
He once again gets reborn into a female and is named Ellie. She thought she had filled her purpose when she lived as Bailey. She goes through this life looking for Ethan but also working as a K9 unit with Jakob. When Jakob gets injured while chasing a criminal, Ellie is handed over to the self conscious Maya and spends the rest of her life with her. He gets reborn as a male named Buddy.
He had thought saving and finding people had been his purpose. He gets adopted by Derek and is given to his girlfriend, Wendi, as a present. They called him Bear. They kept him tied up outside and forgot to feed him and give him water. The neighbor told the authorities. The authorities then came and told them to take care of their pet or they would be arrested and after they left, Victor (Wendi's mom's boyfriend) took Bear and drove him far away from them and left him abandoned on the street. Bear began to walk and he realized where he was.
He meets this girl who has Hannah's scent all over her. He finds the scent of Jasper, Ethan's donkey, in a driveway and races down the driveway to find the Farm. He runs into an older version of Ethan and Ethan brings him home. He renames him Buddy. Buddy goes back to the park a few days later and runs into the same girl again but this time, he follows her home. He then runs into Hannah and when Ethan came to pick him up, Hannah and Ethan were brought back together and got married. Ethan dies of old age. He had fulfilled his purpose.