Mrs. Brisby, a widowed field mouse, lives in a cinder block with her children in a field on the Fitzgibbons' farm. She prepares to move her family out of the field as plowing time approaches, but her son Timothy has fallen ill. She visits Mr. Ages, a friend of her late husband, Jonathan, who diagnoses the illness as pneumonia, provides Mrs. Brisby with medicine, and warns her that Timothy must stay inside for at least three weeks or he will die. On her way home, Mrs. Brisby befriends Jeremy, a clumsy but friendly crow. They both narrowly escape from the Fitzgibbons' cat, Dragon.