The protagonist of Italo Calvino’s novel is, as the title indicates, one person who becomes two people. He begins as the Viscount Medardo of Terralba but, through a battlefield injury, is divided into good and evil selves. The first “half” who returns to his Italian home is the evil persona. The other half is rescued from the battlefield but remains there, a positive presence in everyone’s life. The “Bad ‘Un” in Terralba commits numerous sadistic acts; he especially enjoys bifurcating other things, includes plants and animals. His tactics while amorously pursuing Pamela, a lovely peasant girl, confirm his sadism. The Good ‘Un, having been healed by hermits, dedicates himself to the healing vocation. Inevitably he returns to confront his other, evil half, but his excessive virtue rubs some people the wrong way. The reunion of the opposing selves brings the story’s resolution.

The narrator, a boy about eight years old, is Medardo’s nephew. His astute observations help the reader make sense of the confusing events. Allowed free rein through Terralba’s territory, he fills the role of witness more than active participant.

Trelawney is an English physician who had been shipwrecked on Terralba’s coast. The elderly doctor boasts of his earlier sailing on memorable voyages, such as that of Captain Cook. He retains older English styles, clothes, and accessories, and the accompanying manners. With his profession of physician eclipsed by his heavy drinking, he conducts dubious scientific research.

Ezekiel is the leader of community of Huguenots on Terralba’s outskirts. Along with their exile goes deprivation and poverty, echoed in his pessimistic views.

Esau is Ezekiel’s son. Decidedly impious, he counts among his vices smoking, drinking, and cheating at cards.

Galateo is one of many lepers in a nearby community; they who try to live to the fullest through constant partying.

Pamela is the object of Medardo’s affection. An innocent, lovely peasant girl, who enjoys caring for animals, her simple demeanor covers a perceptive nature. Hiding in a cave to escape the predatory Bad ‘Un, her meeting with the Good Un sets things in motion for their eventual reunification.