David is under pressure at work. His project is going wrong and his boss is not impressed. Then he starts to see things. A girl is stabbed right in front of him on the tube but only he notices. There is no commotion, no ambulance, no police, no blood. Worse still there is no body and no murderer. Work pressure? Hallucination? Obviously. Then it happens again but this time he is the victim. Except he isn't dead and another girl who was helping him to escape realises he isn't a "tourist" after all and she suddenly disappears. Thus begins a chase through the streets of London and through time itself culminating in a mind-bending paradox that threatens both David's sanity and the future of London.