While sinister Lord Luxon makes himself at home in twenty-first century Manhattan, Peter and Kate, aided by Gideon, pursue The Tar Man through the streets of eighteenth-century London, when history is at its tipping point.
When an attempt to bring Peter and Kate back to their own time is bungled, Peter finds himself stranded in 1763 while The Tar Man, a villainous eighteenth-century criminal, returns with Kate to twenty-first-century London.
Ignored by his father and sent to Derbyshire for the weekend, twelve-year-old Peter and his new friend, Kate, are accidentally transported back in time to 1763 England where they are befriended by a reformed cutpurse.