It seems to Mrs. Brisby, the widowed head of a family of field mice, that her youngest son must die, either by the farmer's spring plough or of pneumonia in his flight to safety. In her quest for a cure she frees a young crow from some string in which he has foolishly tied himself, at the mercy of the farmer's cat Dragon. In return for her risking her life to save his, he takes her to the creature all birds know is the wisest: a great owl. Owls eat mice, but when this owl learns Mrs. Brisby's name he sets her on a path to earning a noble solution to her predicament - which is the secret of NIMH...