When the mad philosopher Quincas Borba dies, he leaves to his friend Rubiao the entirety of his wealth and property, with a single stipulation: Rubiao must take care of Quincas Borba's dog, who is also named Quincas Borba, and who may indeed have assumed the soul of the dead philosopher. Flush with his newfound wealth, Rubiao heads for Rio de Janeiro and plunges headlong into a world where fantasy and reality become increasingly difficult to keep separate.