In Seattle, an aspiring Formula One race car driver named Denny Swift adopts a golden retriever puppy he names Enzo, after the founder of Ferrari. Enzo, narrated by a wise and philosophical inner voice, shows a keen understanding of human emotions and a belief that he will be reincarnated as a human after he dies. Enzo carefully observes the nuances of Denny's life, learning about the human condition through the lens of what he learns from television, especially racing. The bond between Enzo and Denny is not just that of a man and his dog but evolves into a deep, almost spiritual companionship. Enzo becomes Denny's closest confidant and supporter, especially as Denny faces various life challenges, including his burgeoning racing career.

Denny's life takes a significant turn when he meets Eve, a schoolteacher, and they quickly fall in love and marry, eventually having a daughter named Zoe. Enzo, with a mix of jealousy and protectiveness, watches this change in Denny's life with a thoughtful eye. He remains loyal and comforting through personal and professional upheavals, providing a unique perspective on human life and relationships. As Denny's career and personal life begin to intertwine and face various obstacles, Enzo's unwavering support and reflections on these events underscore the profound impact of his presence in the family's life, demonstrating the depth of his devotion and the significant role he plays in helping them navigate through their trials.