While continuing to help his classmates solve their problems, Humphrey, pet hamster of Longfellow School's Room 26, faces many surprises, like rolling in a hamster ball, a substitute janitor who might be an alien, and the possibility of Mrs. Brisbane retiring.

After learning about Sherlock Holmes, Humphrey the classroom hamster follows clues to try and discover why Mrs. Brisbane is gone and Mr. E, a fun but not very educational substitute, is taking her place in Room 26 at Longfellow School.

"During a creative writing unit at Longfellow School, the students in Mrs. Brisbane's class practice using their imagination with their very own writing journals--and Humphrey finds out that writing from his imagination is harder than it looks"--

"Humphrey helps the students of Room 26 find a missing dog"--