Rasco and the Rats of NIMH

Blurb

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. During his trip, Timothy meets Racso, the son of Jenner. 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, flooding the entire area. Racso, Timothy, and the entire rat colony must observe and sabotage the dam construction before the valley is underwater.