Jessica Allendon is bored and Googles her name. Weirdly, she finds another girl, same age, same name, also living in London. They arrange to meet. At the designated time and place, Jess sees the girl, shock registering on both their faces as they realise they look identical. They shake hands and in that instant are catapulted into each other's worlds. Jessica finds herself somewhere which looks like the London of 50 years ago, but the year is still 2008. In this parallel London, the history is different, key war memorials are missing, and the Jessica whose life she now inhabits was involved in a dark and sinister conspiracy. Jess must convince everyone she is the same girl, at all costs, if she wants to get back to her London - alive.