The Secret of NIMH 2: Timmy to the Rescue
Seeking help, they visit the Great Owl.  They learn that a caterpillar named Cecil has teamed up with Jeremy, the crow from the first movie, to trick people into paying them money.  Jeremy and Cecil take the two mice to NIMH where they find that two other mice, Justin and Brutus.  They also learn that Dr. Valentine, the head scientist, has made Martin crazy.  He planned to use the lab rats and a flock of ravens to take over Thorn Valley.