"So," Mayumi started, "Let me get this straight, you're going to make this Pollyjuice potion anyway, because the hair is definitely Slytherin, and Malfoy probably know something about it?"
They nod.
"And you want me to help blow up someone's potion, so Hermione here can sneak in to steal something." Mayumi sighed, "Why not? I'll have fun."