Because of the rats' relationship with Jonathan, 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 the rats are too big 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 cat's 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. Mrs. Brisby then escapes from the cage and runs off to warn the rats.