What would you do if someone you knew disappeared right before your eyes?

Dowd, Siobhan (2008). The London Eye Mystery. 322 pages. Grades 5-8.

During his visit to London, Salim's cousins, Ted and Kat take him to ride on the London Eye. While waiting in line, they are approached by a stranger who offers them one ticket for the ride. Ted and Kat suggest that Salim take the ticket, which turns out to be a mistake. They watch as Salim walks into the pod that will carry him around the wheel, but when it opens again Salim has vanished! Ted and Kat must work together to solve the mystery of Salim's disappearance.