Study Guide

Mrs. Frisby and the Rats of NIMH Chapter 12

By Robert C. O'Brien

Chapter 12


  • Mrs. Frisby can only read a little bit, but she reads enough to wonder where or what NIMH is.
  • Her curiosity about the rats is overwhelming and she wants to go explore all over their digs
  • She opens the door to go exploring, but decides that snooping isn't very polite (indeed!), so she returns to the library and shuts the door. 
  • When she resumes examining the board, she sees that the rats have written amounts of Oats, Wheat, Corn, and Seeds.
  • And now she's more confused than ever, of course.
  • As she is puzzling this over, a small girl rat walks in and introduces herself as Isabella. 
  • Mrs. Frisby asks what NIMH is and Isabella says she doesn't know what it is, but that the older rats came from there and no one wants to go back. 
  • Sort of out of nowhere, Isabella declares that she wants to marry Justin. Um, good for her?
  • Mrs. Frisby is more interested in the Plan than in Isabella's love life, however, and asks her what the Plan is. 
  • Isabella says that her Mom doesn't like the Plan, but that they're gonna go along with it, unlike Jenner and his friends, who were unpopular in the colony. 
  • Mrs. Frisby asks who Jenner is, and Isabella quickly (and mysteriously) says that he left. 
  • Just then, Nicodemus, Mr. Ages, Justin, and another rat come into the library.