The Rescuers. Margery Sharp. 1991.

“You all know the Black Castle,” began the Secretary of the Prisoners’ Aid Society. Every mouse in the hall shuddered. And as she told of her daring plan to rescue the poet from its dark walls, they all sat in stunned silence.

So it was that three brave mice - pampered Miss Bianca, Bernard the good-hearted kitchen boy mouse, and the sturdy sailor mouse, Nils, set out on their hair-raising attempt to rescue the poor, languishing poet.