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. The book would be followed by a sequel published in 1990, R-T, Margaret, and the Rats of NIMH. A review from the University of Chicago's Center for Children's books states that "Conly has completely mastered the bucolic tone of the first book", and that "characterizations all around are more detailed than in O'Brien's book". Story 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 begins receiving the same accelerated education as the rat children, Racso, coming from a colony of savage urban rats, has trouble adjusting to life in a cultured town of rodents. Racso is also burdened by his family history, as his father deserted the rats' previous colony, placing them in danger of extinction. Life in Thorn Valley is suddenly threatened when humans begin planning to build a dam there, which will flood most of Thorn Valley and destroy the rats' colony. The rats set a complex plan into motion to reprogram the developers' computers and sabotage the project. Connections to previous works Mrs. Frisby and the Rats of NIMH Racso and the Rats of NIMH is a direct sequel to the Newbery Medal-winning book Mrs. Frisby and the Rats of NIMH by Jane Leslie Conly's late father, Robert C. O'Brien. Conly wrote her sequel long after O'Brien's death in 1973, so even though Conly's book attempts to answer many of the open-ended questions posed by the original, it is still Conly's work and not O'Brien's. One of the most anticipated events of the first book was the possibility of Mrs. Frisby's children (Teresa, Martin, Timothy, and Cynthia) having grown up to visit the rats themselves and partake in adventures