Morning rush hour on the London tube. Laurie Bateman is on her way to work when she witnesses a terrible accident. Only later does it dawn on her that what she has seen is potentially much more sinister.Compelled to investigate, Laurie breaks into the Underground at night to look for clues. The ambush comes out of nowhere. In serious danger she is forced to flee for her life through pitch black tunnels and deserted stations.The hunter has become the hunted.