Robert C O'Brien

Having no one to help her with her problems, a widowed mouse visits the rats whose former imprisonment in a laboratory made them wise and long lived.

On her tenth birthday, Ellen wakes up to find a silver crown on her pillow; a few minutes later her house burns up and her parents disappear, and she is launched on an adventure involving a trek through the woods, a castle full of brainwashed captives, and the powerful Hieronymus Machine which wants her crown.

Three young people find themselves caught up in a love triangle after a disaster has wiped out most of civilization.