In the deep jungles of "Darkest Peru", a British geographer discovers a previously unknown species of bear. He learns that the bears are highly intelligent and that they have a deep fondness for marmalade. He names them Lucy and Pastuzo and gives them his hat as he leaves, telling the bears that they are always welcome if they wish to go to London.

Forty years later, the two bears are living in harmony with their orphaned nephew until an earthquake destroys their home, forcing them to seek shelter underground. Pastuzo fails to reach the shelter in time and is killed by a falling tree. Lucy encourages her nephew to go and find solace in London, while she moves into the Home for Retired Bears.