Huby, the strange boy from The Mystery Under Third Base, appears just in time to help Alex Cooper prove that he did not accidentally murder his hated math teacher on Halloween. And what is a Green Goblin doing in town?

By November 1st, the whole town believed that Alexander Cooper, age 11, had murdered The Worm on Mischief Night. In fact, no one had actually murdered the math teacher, Mr. Wormstead, known as The Worm. However, The Worm's mailbox did blow up, and he may have been pushed down the stairs of his front porch on that cold night before Halloween. In fact, no human actually blew up the mailbox or pushed him. The Worm wasn't even pushed down the stairs, exactly, but an old man plodding along with his old dog, thought he saw a goblin on the porch just before the mailbox exploded. Then Mr. Wormstead ran out, tumbling down his long, steep front staircase. Alex wore a goblin costume for Halloween; exactly like the goblin seen at The Worm's house that night. So, naturally, everyone immediately thought of Alex Cooper.