Snap of the Super-Goop: A Branches Book (The Notebook of Doom #10) (10)

Alexander keeps seeing monsters he has previously conquered, but every time he gets close they disappear and his friends are beginning to think he is delusional--but when one of their teachers turns into a blob of super-goop right before their eyes they realize the team is dealing with a shape-shifter, and it is after the Notebook of Doom.