 A prehistoric aquatic creature like a huge crocodile appears in a London swimming pool, eats a life guard, then vanishes. Later a special forces diver vanishes, but then the diver s bones turn up in a flooded basement in a town some way to the south west. Nick Cutter predicts that incidents will occur at places on a straight line through these two locations on the map of southern England. Eventually Cutter is allowed to go through an underwater anomaly, tethered by a safety rope a mile long. Finally, amid a prehistoric landscape, he meets his long missing wife.