No one pays attention to William Bell--not even when he shows up in Room 101 carrying a huge volcano. But when he makes a bet with the school bully that his class will win the Scariest Costume Contest, everyone pays attention. In fact, the whole class is furious at William for making such a stupid bet.
Now William has to find the scariest costume in the world--or else! Can his quick thinking--and his volcano--save Halloween? Or will disaster strike Room 101?