An encounter with an anti-gravity machine catapults Peter Schock and Kate Dyer back to the 18th century and sets in motion a calamitous chain of events. While a massive police hunt gets underway to find the missing children in the 21st century - in 1763 a hardened criminal, the Tar Man, steals the anti-gravity machine and disappears into the London underworld. Stranded in another time and forced to chase the Tar Man to his lair, Peter and Kate find a friend and guide in reformed cutpurse, Gideon Seymour...