Racso and the Rats of NIMH is the 1986 sequel to the popular book, Mrs. Frisby and the Rats of NIMH, written by Jane Leslie Conly. It continues where the previous book left off. In Racso and the Rats of NIMH, the Rats of NIMH have developed a self-sustaining community in Thorn Valley, where they are completely isolated from humanity. Timothy Frisby, the youngest son of Mrs. Frisby, travels from his family's home to Thorn Valley. (Although his mother is an ordinary mouse, Timothy has inherited the extremely high intellect and long lifespan of his father, NIMH escapee Jonathan.) During his trip, Timothy meets Racso, the son of Jenner (a rat of NIMH introduced in first book who is widely considered to be a traitor). Timothy and Racso arrive at Thorn Valley, but while Timothy integrates and be