After relating all of the horrible things the school custodian, Fester Smudge, is known to have done, a student whose locker won't open needs Mr. Smudge's help.
The students in Mrs. Green's class get a bit nervous when she announces she is going to bring in a class pet but will not reveal what it is--letting their imaginations run wild.
On the first day of a new school year Mrs. Green's imagination runs wild as she thinks of all the horrible things she's heard about her new class, including that they've sent their previous three teachers into early retirement.