Schoolgirl Jade Robinson, beautiful and intelligent, witty and funny, is looking forward to her 14th birthday and a very special present. But her father, an amateur astronomer and head of science at a London boys' school, discovers that a giant comet is on a collision course with the earth. He fears that it will strike the world sometime in 2017. No one listens to his warnings until it is too late. As civilisation and society breaks down after the comet, the Robinson family turn their home into a Citadel. Jade puts down her schoolbooks and picks up her rifle to defend her family against the barbarians and the wolves at their gates.