The Cave is the third book in the chapter book series Museum Mysteries. Claira, Ariel, and Kimberly have been on two adventures with Bast, a cat with magical powers, and her friend Maximus, a large black Labrador Retriever with a bionic eye. Three young boys are missing in Italy and Bast needs the girls' help to rescue them. Will they agree to enter the portal in the closet with Bast?