 The Thornberrys are driving in the Andes Mountains in Peru on the way to visit Dr. Spinoza the world s foremost authority on vampire bats. This is a special trip for Marianne who was a student of Dr. Spinoza s twenty years ago. On the way Eliza starts reading about bats and her movie memories about vampires starts spooking her a bit. Dr. Spinoza lives in a remote, big castle and he is not at all like Marianne remembers. Everything about him gets Eliza s imagination going and Debbie sees it as a chance to have some fun at her sister s expense.