Fact1: Brisby prepares to move family out of field, Fact2: Jeremy takes her to visit Great Owl, Fact3: Great Owl tells her to visit group of rats on farm, Fact4: experiments boosted intelligence enabling them to escape as well as extending lifespans and slowing aging process, Fact5: Justin Because of husband 's relationship with agree to help Brisby move home rats
Output: Mrs. Brisby, a timid widowed field mouse, lives in a cinder block with her children in a field on the Fitzgibbons farm. She prepares to move her family out of the field as plowing time approaches, but her son Timothy has fallen ill. She visits Mr. Ages, another mouse and friend of her late husband, Jonathan, who diagnoses Timothy with pneumonia and provides her with medicine. Mr. Ages warns her that Timothy must stay inside for at least three weeks or he will die. On her way home, she encounters Jeremy, a clumsy but friendly crow. They both narrowly escape from the Fitzgibbons cat, Dragon. The next day, Mrs. Brisby discovers that Farmer Fitzgibbons has started plowing early. Although her neighbor Auntie Shrew helps her disable his tractor, Mrs. Brisby knows she must devise another plan. Jeremy takes her to visit the Great Owl, who tells her to visit a group of rats that live beneath a rose bush on the farm and ask for Nicodemus, their wise and mystical leader. Mrs. Brisby enters the rose bush and encounters a aggressive guard rat named Brutus, who chases her away. She is led back in by Mr. Ages, and is amazed to see the rats use of electricity and other technology. She meets Justin, the friendly Captain of the Guard, and Jenner, a ruthless, powerhungry rat opposed to Nicodemus, and finally Nicodemus himself. From Nicodemus, she learns that many years ago her husband, along with the rats and Mr. Ages, were part of a series of experiments at a place known as NIMH, the National Institute of Mental Health. The experiments boosted their intelligence, enabling them to escape, as well as extending their lifespans and slowing their aging process. However, they are unable to live only as rats, needing human technology to survive, which they have only accomplished by stealing. The rats have concocted The Plan, which is to leave the farm and live independently. Nicodemus gives Mrs. Brisby an amulet called The Stone, which gives magical power when its wearer is courageous. Because of her husbands relationship with the rats, they agree to help Mrs. Brisby move her home. First, they need to drug Dragon to sleep so that they can complete the move safely. Only Mrs. Brisby can do this, as only mice are small enough to fit through the hole leading into the house; Jonathan was killed by Dragon in a previous attempt, while Mr. Ages broke his leg in another. That night, she puts the drug into the cats food dish, but the Fitzgibbons son Billy catches her. While trapped in a birdcage, she overhears a telephone conversation between Farmer Fitzgibbons and NIMH and learns that the Institute intends to exterminate the rats the next day. She escapes from the cage and runs off to warn the rats. The rats are moving the Brisby home, with the children inside, using a rope and pulley system during a thunderstorm. Jenner, who wishes for the rats to remain in the rose bush, sabotages the ropes with his reluctant accomplice Sullivan, causing the assembly to fly apart and kill Nicodemus. Mrs. Brisby arrives and tries to convince the rats that NIMH is coming and they must leave, but Jenner attacks her and attempts to steal the amulet. Sullivan alerts Justin, who rushes to Mrs. Brisbys aid. Jenner mortally wounds Sullivan and engages Justin in a sword fight, which ends with Sullivan killing Jenner before dying himself. The Brisby house begins to sink into the mud, but Justin and the rats are unable to raise it. Mrs. Brisbys will to save her children gives power to the amulet, which she uses to lift the house and move it to safety. The next morning, the rats have departed for Thorn Valley with Justin as their new leader, and Timothy begins to recover. Jeremy eventually meets Miss Right, another crow who is just as clumsy as he is, and the two fly away together.