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.

In a series of letters a student laments the absence of her teacher and daily routine, but she soon realizes there are benefits to mixing things up, and that perhaps having a substitue teacher is not so bad afterall.

"Milton Worthy can't wait for his class trip to the city zoo. But little does he know that Noah--part time classroom pet ferret, part time evil mastermind--has escaped and stowed away on his school bus. Good thing that Mrs. Worthy, ace world-saving, member of the super-secret Society of Substitutes, is along for the ride! Will Milton and his super-substitute mom be able to stop the zoo from running completely wild?" -- Page [4] of cover.

It's Christmastime and Jack's new substitute teacher, Mr. Clausen, teaches the class how to make paper snowflake wishes, all the while reminding the class of another gentleman with a long white beard who enjoys a snack of milk and cookies.

"Keep your friends close and your enemies closer! When Snowball, the puffball hamster in Ms. Kim's classroom, accidentally sips the teacher's leftover protein shake, she transforms into a monster like Beacher Elementary School has never known before. It's all hands on deck to stop Snowball before it's too late. And to do that, Milton Worthy is going to do have to team up with Noah, the part-time classroom ferret, full-time evil mastermind! Will Milton...