"Mrs. Frisby and the Rats of NIMH" is a children's novel written by Robert C. O'Brien. The story follows a field mouse named Mrs. Frisby who must save her family from a farmer's plow. To do this, she seeks help from a group of genetically modified rats who escaped from a laboratory called NIMH. The rats, led by Nicodemus, possess advanced intelligence and have developed a society of their own. As Mrs. Frisby learns about their past and struggles, she discovers themes of bravery, friendship, and the importance of community. The book combines adventure with moral lessons, making it a beloved classic.