Sam just got a hamster for a pet and she is not really impressed, but after reading a book about mythological creatures, Sam gets some ideas for exciting pets.
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.
Humphrey the hamster is puzzled when unfamiliar students fill Mrs. Brisbane's classroom at summer's end, but he soon learns that his friends from last year are fine and that the new class needs his special help.