Robert C. O’Brien’s 1971 Mrs. Frisby and the Rats of NIMH is a standalone children’s SF novel. O’Brien wrote no sequels.
Mrs. Frisby (a mouse) and her children (mice) have taken shelter in a cinder block near one of the fields owned by farmer Fitzgibbons. Winter is over and plowing season is approaching. The widow Frisby must move her children before a plow smashes into their home.
In previous years, Mrs. Frisby had no trouble relocating her family before plowing season. This year is different.