Double cross

"In this fourth and final book, tween twins Cassie and Caitlyn Waters are excited to be returning to their hometown, San Antonio, on a class trip. But as they reach their destination, trouble finds them as quickly as a vision, and one of their friends soon disappears. Using their Sight and their street smarts to try and save the day, the twins also begin to see things they didn't expect -- a man in captivity who looks exactly like their father's...