Tom knows all about stepmothers from the books he's read. They do all sorts of horrible things. In fact, they aren't really stepmothers at all. They are StepMONSTERS! So when his dad's new friend Lulu comes to tea, Tom is convinced she will turn out to be a stepmonster. She might not look like a stepmonster. (Her hair looks like it's been spun from gold.) And she might not act like a stepmonster. (She likes all of the same things that Tom does - manatees and moles and woodlice and playing Snap for hours.) But maybe that's just a clever disguise.