The students in the third grade class at Cartier Elementary School are so difficult to discipline that all of their teachers have given up. But their new teacher, Mrs. Lefroy, is different (and that's the least we can say). Fresh from Transylvania, she's moved into a strange house in Ville-Cartier, and she wears a mysterious brooch whose brilliant glow is as green as her eyes. Could it be that Madame Lefroy is a vampire, despite her polka dot dress?