This time around, Leo San Juan, Don Andrés, Teodora and Alebrije come to Guanajuato to try to stop the mummies – who have inexplicably risen from the dead – and rescue their friend Xóchitl. With the help of Luis, a friend they meet in the city, Leo uncovers the terrible secret of the aristocratic Rousseau, while the rest of the team realize they have fallen into a trap.