Sixteen-year-old AJ Flynn holds a key in his hand. It has his name and date of birth on it. But it's a key to a door that leads to where? Or when? On the other side of the door is a tumbledown house, a city booming with trade, and a murder mystery that echoes through the centuries. AJ steps through the door and finds himself at the centre of it all. It is London and it is 1830. Life is tough in 1830 - sickness, murder and crime abound - but is it so different from the London of now that AJ and his friends know? AJ needs to find the answers to the mystery - and decide where he belongs.