Ted and Kat watched their cousin Salim board the London Eye, but after half an hour it landed and everyone trooped off --- except Salim. Ted and his older sister, Kat, become sleuthing partners, since the police are having no luck. Despite their prickly relationship, they overcome their differences to follow a trail of clues across London in a desperate bid to find their cousin. And ultimately it comes down to Ted, whose brain works in its own very unique way, to find the key to the mystery.