Courtney Crumrin and the Night Things #3

Plot

When Courtney's teacher goes on maternity leave, the class gets a substitute to toy with and torment! But the new instructor isn't everything she appears to be, and may have more in common with Courtney than either of them could possibly imagine! What is her link to the mysterious Coven, and what does Uncle Aloysius have to do with the evil spirit that's wreaking havoc on the town?