Irving and Muktuk have arrived from Yellowtooth in the frozen North to their new home in the Bayonne, New Jersey, zoo. There they meet another polar bear, Roy, who tells them about his life outside the zoo. Roy goes home every night at six when the zoo closes. After a week of swimming, eating fish and the occasional muffin thrown to them by zoo visitors, playing, and taking naps, Irving and Muktuk feel bored and restless. They decide to explore life outside the walls and go in search of Roy and more muffins. Soon their escape is discovered and the zookeepers, the zoo director, and the police are called. Are these polar bears to be trusted?