Mrs. Frisby was a mouse whose husband, Jonathan, died. And so, when she had a serious problem, she had no one to turn to help. That is she had no one until a friendly crow took her to a wise old owl, a frightening creature for a mouse to visit. Then at the owl's suggestion, she went to visit the rats who lived under the rosebush. This, too, was a daring undertaking. The rats were an odd and unknown lot. Everyone on Mrs. Fitzgibbon's farm knew the rats did strange things.
Yet nothing Mrs. Frisby had heard of the rats was as strange as the truths she discovered about them, and also about her dead husband. Neither these rats nor her husband were ordinary creatures. All had been imprisoned for several years in a labrotary known as NIMH, where various injections had made them wise, long-lived, and inventive. The rats were indeed able to help Mrs. Frisby. And she in turn rendered them a great service.
As to the end of the story: Mrs. Frisby had her problem solved. But the rats, well that's something else again.
P.S. Great story for kids learning in Middle School. Has around 233 pages.