Ant's premonition comes true when Liam's house is destroyed one Saturday evening – but not by a dreaded laser bolt from space. Instead, a massive sinkhole opens up and plunges the house deep underground with Liam and Madison inside. Could this be the work of eight-year-old Caleb, the mysterious, all-powerful, long-lost son of Ant's chauffeur? If so, he's created an incredible and frightening underground world...