Silver Storm - Red Fever trilogy, book 3

A terrible virus has wiped out most of the human population and Scotland is now a wasteland. Toby and his family are being held hostage on the island of Orkney by a terrifying militia group called the Corporation. Toby knows he and his friend Tash must escape and find their way toEdinburgh if they are ever to bring about an end to the carnage that the red fever has caused.