Bianca and Bernard, agents for The Prisoners` Aid Society of Mice, rescue prisoners and outwit villains in this enchanting story, made world-famous by the Walt Disney film.

The Prisoners` Aid Society of Mice discusses the proposed rescue of a Norwegian poet from the terrible Black Castle.

Miss Bianca, the pet white mouse belonging to the Ambassador`s son, is sent to Norway on a mission to recruit the bravest Norwegian mouse she can find. She finds Nils, and brings him back triumphantly. Then she, Nils, and Bernard, a pantry mouse who falls in love with her, set off for the Black Castle.

They set up home in a mousehole in the Chief Jailer`s room, and narrowly avoid the jaws of Mamelouk the cruel Persian cat. Eventually they trick the cat and the jailer, and get into the prisoner`s cell. A dramatic rescue via an underground river, and they are all free and the Nils and Miss Bianca medal for bravery is struck in the mice`s honour!