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 Pictures. Could He Really Be Alive? And Can They Use The Clues They See To Save Him Before It's Too Late?--amazon.com.