Mrs. Frisby and the Rats of NIMH is a 1971 children's book by Robert C. O'Brien. Illustrated by Zena Bernstein, it won the 1972 Newbery Medal. A film adaptation, The Secret of NIMH, was released in 1982.

The novel relates the plight of a widowed field mouse, Mrs. Frisby, who seeks the aid of a group of former laboratory rats in rescuing her home from destruction by a farmer's plow, and of the history of the rats' escape from the laboratory and development of a literate and technological society.

The work was inspired by the research of Dr. John B. Calhoun on mice and rat population dynamics at the National Institute of Mental Health.[1]

Plot summary

Mrs. Frisby's son, Timothy, falls ill with pneumonia just as the farmer Mr. Fitzgibbon begins preparation for spring plowing in the field where the Frisby family lives. Normally she would move her family, but Timothy would not survive the cold trip to their summer home. Mrs. Frisby obtains medicine from her friend Mr. Ages, the older white mouse. On the return journey, she saves the life of Jeremy, a young crow, from Dragon, the farmer's cat - the same cat who had killed her husband. Jeremy advises her to seek advice from an owl who dwells in the forest. Jeremy flies Mrs. Frisby to the owl's tree, but the owl says he can't help until he finds out that she is the widow of Jonathan Frisby. He suggests that she seek help from the rats who live in a rosebush near her home.

Mrs. Frisby discovers the rats have near-human intelligence, with a literate and mechanized society. They have technology such as elevators. They have tapped the electricity grid to provide lighting and heating, and have acquired other human skills, such as storing food for the winter. Their leader, Nicodemus, tells Mrs. Frisby of the rats' capture by scientists working for a laboratory located at NIMH and the subsequent experiments that the humans performed on the rats, which increased the rats' intelligence to the point of being able to read, write, and operate complicated machines, as well as enhancing their longevity and strength. This increased intelligence and strength allowed them to escape from the NIMH laboratories and migrate to their present location. Jonathan Frisby and Mr. Ages were the only two survivors of a group of eight mice who had been part of the experiments at NIMH, and who had escaped with the rats. Out of respect for Jonathan, Nicodemus agrees to help Mrs. Frisby's family.

The rats are preparing to abandon their lifestyle of dependence on humans, which some rats regard as theft, for a new, independent farming colony. Shortly before Mrs. Frisby's arrival, a group of seven rats led by a rat named Jenner left the colony because they disagreed with this shift, and are presumed to have died in an accident at a nearby hardware store. This incident has attracted the attention of a group of men, who never identify themselves, and they have offered to exterminate the rat colony on Fitzgibbon's land free of charge for him.

Mrs. Frisby overhears the Fitzgibbons discussing the men and reports back to the rats. Thanks to Mrs. Frisby's warning, the rats have time to plan their escape. The successful house move allows the mouse family to remain while Timothy recovers before moving to their summer home.

Related works

O'Brien's daughter, Jane Leslie Conly, wrote two other novels based on the rats of NIMH. Racso and the Rats of NIMH tells the story of a city rat who runs away to join the new colony, befriending Timothy, while saving the colony from a flood along the way. In R-T, Margaret, and the Rats of NIMH, the rats rescue two lost human children who in turn help to save the colony before winter.

In 1982, the animated film The Secret of NIMH was released, directed by Don Bluth. The film adds a mystical element completely absent from the novel. Additionally the character of Jenner is made a villain; he kills Nicodemus, and two other characters are killed in a sword fight. Additionally, Mrs. Frisby's name was changed to Brisby.


Preceded by
Summer of the Swans
Newbery Medal recipient
Succeeded by
Julie of the Wolves
Preceded by
The Trumpet of the Swan
Joint winner of the
William Allen White Children's Book Award

with The Headless Cupid

Succeeded by

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