Several storylines are interwoven in The Art of Racing in the Rain. Many things come together quickly, and in unexpected ways, to bring closure to all the issues addressed in the book.
Enzo, the dog and narrator of the story, dies in Denny's arms, sparing him the ordeal of going to the vet and asking to have the dog euthanized. Enzo is grateful to be able to die on his terms, confident that he will come back to live again, as a human the next time.
He died that day because his body had served its purpose. His soul had done what it came to do, learned what it came to learn, and then was free to leave.
Eve's parents agree to concede custody of Zoe back to Denny. As Denny is baking cookies to celebrate Zoe's return home, a phone call from Luca Pantoni again offers Denny the job as a test driver for Ferrarri in Italy. Denny realizes he is now in a position to be able to accept the job, but still questions why Luca is offering it.
Luca explains that when his wife died, a near-stranger saved him, emotionally, by offering him a job as a driver with Ferrari. Luca is pleased to be able to pass the opportunity forward by now helping another widower find life after the passing of his spouse.
In the final scene in the book, Zoe approaches her father after he has completed a driving session in Italy. She wants Denny to sign an autograph for a young boy she has encountered who says he is Denny's biggest fan. When Denny asks the boy his name, the answer is, "Enzo."