The book is set as a series of journal entries, where the unnamed narrator goes back and forth between his life with the rats and his work, in a low-level job at a company that his father used to own. In these entries, the young man dwells on the hatred he feels for his boss, the stresses of caring for his aging mother, a nameless girl he becomes fond of and above all the families of rats which he has befriended and which he uses for company and companionship.