Enzo is a lab terrier mix plucked from a farm outside Seattle to ride shotgun with race car driver Denny Swift as he pursues success on the track and off. Denny meets and marries Eve, has a daughter, Zoë, and risks his savings and his life to make it on the professional racing circuit. Enzo, frustrated by his inability to speak and his lack of opposable thumbs, watches Denny's old racing videos, coins koanlike aphorisms that apply to both driving and life, and hopes for the day when his life as a dog will be over and he can be reborn a man. When Denny hits an extended rough patch, Enzo remains his most steadfast if silent supporter.