A virus carried by flies is rampant in the world. Giant swarms of insects sweep away everything in their path, devouring people and animals, and infecting the survivors with a terrible disease. The infrastructure has been destroyed, cities have turned into ruins. The few survivors are hiding in the wilderness. Among them is a scientist who endlessly tells his daughter Nico the legend of a mysterious geological anomaly discovered in Manchester, in the waters of the Merrimack River. When the scientist's wife dies of a virus and he himself is seriously ill, Nico travels to Manchester with his faithful dog Harry. On the way, she meets other guys walking in the same direction. Each of them has its own story, but they are all intertwined in a strange way. The guys are left to connect the found keys, and in this they are helped by the mysterious Delivery Man, who lives life after life in an attempt to direct events in the direction he needs.