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"You must go, Mrs. Frisby, to the rats under the rosebush. They are not, I think, like other rats."
The Owl

This page is about the book Mrs. Frisby and the Rats of NIMH and its literary sequels. If you are looking for the article about the animated film, see The Secret of NIMH.

A 1971 novel by Robert C. O'Brien about lab rats that gained human intelligence through a series of top secret government experiments.

The protagonist of the story, Mrs. Frisby, is a fairly intelligent, but otherwise ordinary field mouse. Mrs. Frisby seeks a way to keep her sick son, Timothy, alive during the spring plowing. He is too weak to move to their summer home without risking his death, but staying would mean certain death because their winter home lies directly in the path of the farmer's tractor. In order to ensure her son's survival, Mrs. Frisby seeks the help of the elusive uplifted rats of NIMH (National Institute of Mental Health).

The first and last third of the book are told from the (third person limited) perspective of Mrs. Frisby while the second third is a long flashback narrated by Nicodemus. The sections of the book focusing on Mrs. Frisby are mostly about trying to stay Home, Sweet Home. The animals in that section are anthropomorphized quite a bit and all of them are rather intelligent, even without being uplifted. Nicodemus' chapters are quite different in tone, almost to the point of Mood Whiplash. His chapters deal with the escape of NIMH, and the animals in this chapter are less human than those of Mrs. Frisby's. If read separately you would be forgiven for thinking it was from a different story. The NIMH chapters examine animal intelligence, the psychological differences and similarities between humans and rats, The Scientific Method, and the philosophical ramifications of stealing.

It was written in 1971 and made into a very loosely adapted animated feature-length film called The Secret of NIMH by celebrated director Don Bluth. The film has mostly eclipsed the novel in terms of popularity and recognition, but the book itself remains a great piece of literature if the Newbery Medal is any indication. After O'Brien's death, there were a couple of semi-official sequels written by his daughter, but the general consensus on their quality and where they fall in the continuity spectrum is variable. [1]


  • Air Vent Passageway: Subverted. It's portrayed realistically with the rats spending over a week exploring the vents with a spool of thread before they know the way out well enough to escape. Rats of course, are also much smaller, lighter and make less noise than humans, which makes the trope more plausible in that respect as well. Even things like the fans used to provide air movement are taken into account. They're not giant and looming, but the strong wind they provide actually blows away lighter animals into other passages and ducts where they can't be reached or even found. The mesh on outside of the vent to prevent debris from entering the ducts provides a significant obstacle, as well, as the rats have much trouble removing it from the inside and are only able to pry open a small enough hole for mice to fit through.
  • Amplified Animal Aptitude: The relative intelligence of ordinary animals almost undermines the NIMH storyline. Even ordinarily stupid animals that have no connection to the rats can easily understand and even embrace concepts such as calendars and marriage. With difficulty they can even be taught literacy, which is a trait that is painted as something extraordinary in the NIMH chapters.
  • Animal Talk: The animals can understand humans and each other, but can't or don't talk to humans. This leads to a bit of Fridge Logic as to where exactly all these animals picked up English, and whether they can understand other human languages automatically as well.
  • Anthropomorphic Shift: The chapters in the original book involving Mrs. Frisby have animals that are more anthropomorphic than the ones involving the rats of NIMH. Ordinary rodents are seen using tools and can understand some very human concepts without much difficulty. It's possible that this is because the NIMH chapters are from the rats' perspective while the rest are from relatively normal Mrs. Frisby's perspective. One would expect Mrs. Frisby to see her fellow non-uplifted animals as being fairly bright.
  • Arcadia: What the rats eventually want to live in.
  • Ascended Extra: Jenner, who is only the leader of a dissenting faction of rats, is only described in flashbacks and not even very well at that. He's killed offscreen and given a passing mention. In the movie, he's given the role of major antagonist and full-on villain, despite him only being pessimistic and argumentative in the novel. Robert C. O'Brien's daughter, and the author of the sequel novels, was highly influenced by The Secret of NIMH, which lead her to Retcon Jenner's death and promote him to a major part of a new character's backstory in the first sequel. He's even shown to be the father of a major character in one novel, which the character tries to hide due to worries over Jenner's controversial opinions. However, he still turns up very rarely, mostly in flashbacks, and is killed off-page during the climax of Racso. A more accurate example of this trope would be Isabella, a very minor character from the first novel who is a major supporting character in Racso and R-T.
  • Author Existence Failure: Robert C. O'Brien died only two years after this book was published. The sequels to the first book are all written by his daughter.
  • Buried Treasure: By field mouse standards, the stash of food Mrs. Frisby finds is this.
  • Bus Crash: A splinter group of rats, which includes Jenner, is killed by an accident at a hardware store. Said group departed even before the main storyline; the event is only described by some tertiary characters and is never shown.
  • Canon Dis Continuity: Despite the novel canon borrowing a couple of minor elements established by the first movie, the movie's sequel The Secret of NIMH 2: Timmy to the Rescue completely ignores Jane Leslie Conly's written sequels.
  • Canon Immigrant: The book's sequel, Racso and the Rats of NIMH, makes several references to elements exclusive to the movie adaption, such as Mrs. Brisby's red cape and the characterization of Jeremy. Ironically (aside from Timmy venturing to Thorn Valley) very little of the book was put into mind for the film's sequel. The sequel takes some very minor elements from the original book, such as referring to Brutus' gentler real persona and the number of mice that survived the escape from NIMH (though this also causes a contradiction with the first film).
  • Carnivore Confusion: The owl declines to eat Mrs. Frisby, and even gives her advice on how to save her son.
    • Moreover, Mrs. Frisby's neighbor and apparent friend is a shrew, and shrews also eat mice.
  • Cats Are Mean: Dragon. A recurring saying among the animals is, "We all help one another against the cat.". Even the owl goes by this.
  • Death by Newbery Medal: Surprisingly Averted, despite this book being mostly about animals. Unless you count the minor character Jenner.
    • The first book had the Frisby children speculate that Justin died during the destruction of the rosebush. The sequels established this death to being that of a previously unmentioned character.
    • Mrs. Frisby does recall overhearing some other woodland creature being shot earlier in the year, and finds its stash of food, although its name and even species are never revealed.
  • Elaborate Underground Base: The rats have one of these, complete with electricity, machinery and running water stolen from the humans that live nearby.
  • Even Owls Have Standards: The old owl who lives deep in the forest preys on rodents, and could most likely make short work of a cat, but he is still of the opinion that Dragon is something that animals should help each other out against. The owl also has a personal sense of hospitality that prevents him from harming visitors in his home, even small, edible, rodent-type visitors.
    • Of course, he might be choosing to help small animals avoid the cat so that he can eat them later, once he's actually hungry...
  • Gone Horribly Right: The result of the experiment on the rats and mice of NIMH.
  • Grumpy Bear: Jenner, was an advocate of continuing to live off humans. He didn't believe that they should curb their stealing to avoid discovery because he didn't think there was any way that humans could truly exterminate all the Uplifted Rats. Neither did he have any faith in the ability of the rats to start and maintain a working civilization. Because of his dissenting opinion he left the rat colony with a number of supporters to create a new colony that was more dependent on humans before the start of the book. It ends badly.
  • Humans Are Bastards: Rats see humans like this in a way, because of their vehement and perhaps irrational hatred towards rats.
    • Also, y'know, because of all that sticking them with needles and shocking them through their feet.
  • Idiot Ball: Let's capture some rats and make them hyper intelligent, then we should make cages that they can physically open and then put written instructions on how to open the cages on them. And heck, since we're already at it we should also teach them how to read.
  • Immortality Begins At Twenty: The offspring of the laboratory-altered rats of NIMH all age at a normal rate for a rat. If they do exhibit the longevity of their parents, it will be the kind that begins at sexual maturity. On the other hand and depending on how you interpret the text, mice exhibit the extended lifespan (perhaps to a lesser extent) from day one. Mrs. Frisby's children are still children at over a year old, a fact that goes unremarked by their mother.
  • Inferred Holocaust: The rats of NIMH increased from a group of 20 rats to 115 rats in only five years. Thorn valley can sustain an estimated capacity of 2000 rats. If the rat population continues to grow at the same rate (about 142% a year), they will hit their maximum sustainable population density in only 8 years. Normally the fact that rats breed like... well rats, is remedied by predation and their own short lifespans, but the rats of NIMH are too smart to prey on and since they've been uplifted, their lifespans are many, many times that of an ordinary rat. These rats are either going to have to invent the world's tiniest condoms or the earth will be entirely overrun by hyper-intelligent rats in less than fifty years. (The sequels indicate that many of the mated Thorn Valley couples have limited offspring, and that many rats choose to focus on scientific pursuits for some years before even considering a family. Timothy and Racso's best friend Christopher often bemoans his only-child status.)
  • Informed Flaw: The unintelligence of non-NIMH experimented animals for one.
  • Intellectual Animal: The entire cast.
  • Kansas City Shuffle: When the NIMH agents come to bulldoze the rosebush on the Fitzgibbon farm, the rats don't defend, fortify or fight for their nest. The rats allow NIMH to destroy their base, but they dig an extra tunnel leading into the forest and use it to evacuate all the rats before NIMH arrives. They then tasked a handful of rats to run back into the nest through the tunnel and then escape through the main entrance, and then back into the tunnel and out again. This lead the exterminators to believe that they had killed or at least scattered a large amount of rats, even though they only saw the same six or seven over and over again. On top of this, the rats destroyed their Elaborate Underground Base before they evacuated, so that it resembled an ordinary rat's nest. The net outcome was that even though the rats had lost their former home, it caused NIMH to mistakenly believe they had taken care of the rat problem and that the rat escapees weren't even very intelligent to begin with.
  • Lamarck Was Right: Averted. The book is actually very good about this. The injections given to the rodents at NIMH to enhance intelligence altered their DNA, and thus the Uplifted Animal trait was passed on to the next generation. The injection to increase lifespan was steroid based, and therefore the rats are uncertain if the effects will be inherited. If they are indeed, then it's a case of Immortality Begins At Twenty for the younger generation because they have up until that point at least grown up at a normal rate of aging.
  • Malignant Plot Tumor: The B plot about the rats of NIMH, which is easily the best-written and most fascinating part of the book.
  • Mayfly-December Romance: Subverted. The experimental treatment given to Jonathan Frisby greatly increased his lifespan, and potentially those of his offspring as well. He would have outlived his wife by quite a number of years, had he not been killed by Dragon, the cat before the start of the story.
  • Most Writers Are Human: The anthropomorphic qualities of the rats of NIMH can be excused due to their greater intelligence and time spent with humans, but even ordinary animals tend to act a lot like people. Mrs. Frisby occasionally mentions marriage and the proper age to marry as if they applied to her, and other rodents in general.
  • Mouse World
  • No Control Group: Averted.
  • Obfuscating Stupidity: The rats of NIMH must exhibit this and pretend to be ordinary rats at all times, lest their intelligence leads discovery and recapture. When moving out of their Elaborate Underground Base, they go through great pains to disguise it as an ordinary rat's nest. They move out all the machinery, destroy all the fancy architecture and fill the whole base with garbage. This was a rush job, and given enough time they would have even destroyed the machinery. In another instance Justin declines to release Mrs. Frisby from a birdcage the conventional way. Instead he opts to disguise her escape as a flaw of the cage rather than opening it deliberately.
  • The Owl-Knowing One
  • Precocious Crush: Isabella's crush on Justin. Introduced in the original novel and a significant sub-plot in the first sequel. He does not encourage it and ends up marrying a rat his own age. Isabella, after doing some painful soul-searching, ends up "special friends" with Racso instead.
  • Rosebush Technology
  • Retcon: Jenner's death in the sequels written by O'Brien's daughter.
  • Rodents of Unusual Size: While the rats of NIMH are nowhere near enormous, they are much bigger than ordinary rats and in fact Mrs. Frisby describes the rat Brutus as being close in size to a tomcat.
  • Sdrawkcab Name: Racso.
  • Sequel Hook: Martin pledges to visit the valley where the rats end up settling one day, possibly with the help of Jeremy the crow. Sadly this was unable to be realized by the original author because of his untimely death.
  • The Scientific Method: Shown accurately in the first book. They even use a control group!
  • Shouldn't You Stop Stealing?: Nicodemus and the vast majority of rats recognize that stealing electricity and such is highly conspicuous and will only get more conspicuous as their population increases. They've even discovered a way to live without having to hijack resources from humans, but at the same time there is a small minority that doesn't fear the repercussions and would rather continue stealing.
  • Shown Their Work: The section narrated by Nicodemus at least. It's very detailed and accurate about The Scientific Method, the inherited effects of the experiments and the psychology of rats.
  • Truth in Television: Part of the reason the section about NIMH is so realistic is because the section was inspired an actual series of experiments done on rodents at NIMH, which is even an actual place
  • Uplifted Animal: The rats of NIMH, Jonathan Frisby and Mr. Ages are all as intelligent as or even more intelligent than humans.
  • What Measure Is a Non-Human?: Nicodemus discusses this issue and postulates that human dependency and the lack of tool use are the reasons rats have stagnated in terms of intelligence and civilization. He theorizes that perpetual stealing from humans would just make life too easy and put rats back into a rut where they don't progress at all and live in total dependency on humans.
  • Writers Cannot Do Math: It's not clear if this is an error on the writer's part or on the character's, but Mrs. Frisby noticed that Jeremy was a young crow, only about a year old, but she doesn't notice that her children are over a year old and are still children.


  1. Though, it should be noted that there seems to be a lot of misconceptions on the net about the actual content of her sequels
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