The book is an autobiographical account of five years in the childhood of naturalist Gerald Durrell, age 10 at the start of the saga, of his family, pets and life during a sojourn on the island of Corfu. The book is divided into three sections, marking the three villas where the family lived on the island. Gerald is the youngest in a family consisting of their widowed mother, the eldest son Larry, the gun-mad Leslie, and diet-obsessed sister Margo together with Roger the dog. They are fiercely protected by their taxi-driver friend Spiro (Spiros "Americano" Halikiopoulos) and mentored by the polymath Dr. Theodore Stephanides who provides Gerald with his education in natural history. Other human characters, chiefly eccentric, include Gerald's private tutors, the artistic and literary visitors Larry invites to stay, and the local people who befriend the family.