In Gideon the Cutpurse, an accident with an anti-gravity machine catapulted Peter Schock and Kate Dyer back to 1763. Now a bungled rescue attempt leaves Peter stranded in the 18th century whilst a terrifying villain, The Tar Man, takes his place and explodes onto 21st century London. Concerned about the potentially catastrophic effects of time travel, the NASA scientists responsible for the situation question whether it is right to rescue Peter. Kate decides to take matters into her own hands, and contacts Peter's father for help. But things don't go as planned, and soon the physical effects of time travel begin to have a disturbing effect on Kate.

Meanwhile, in our century, The Tar Man wreaks havoc in a city whose police force are powerless to stop him...