Skeleton Key by Anthony Horowitz is about a boy named Alex rider who is a spy for M16 and is in Cayo Esqueleto. Alex is pretending to be a bat boy and almost get killed in the process. He is in the room of Alan blank and is going on a mission. He got on a plane and met two CIA agents. Alex is with Troy and the other CIA agent is with a salesman. To CIA agent go in a cave and get killed. Alex gets capered and is brought to a salt mill. He almost gets killed but don't. He is in captivity and there is no way out. If you like the I Survived series you would like Skeleton key.