When Will searches for a prop he can use as an infernal machine (a Victorian time bomb) for a comedy melodrama his class is putting on as a school play, lawyer and sorcerer Titus Croadley realizes this is his chance for revenge. He has a score to settle with Will Sutton, who once interfered with his evil plans. Now the sorcerer creates a real infernal machine - with a real demon trapped inside it.
Croadley arranges for Will to give the infernal machine to Miss Laveau, the English teacher putting on the class play. She is the descendant of a powerful voodoo queen, and has inherited some of her ancestor's secrets - secrets she has refused to share with the sinister lawyer-wizard. Now Croadley plans to get revenge on two enemies for the price of one.
However, things go wrong - for Titus Croadley, and especially for Will, Waldo, Lisa and Uncle Zachary - when Miss Laveau's voodoo powers accidentally bring the demon out of her dreams and into the real world - and out of Titus Croadley's control!
Can Will and his friends save their favorite teacher from the magician's awful slave - or will they join her as the demon's next victims?