Six Days by Philip Webb (author)

In a ruined future, an extraordinary artefact is rumoured to lie buried. Everyone wants it. But why? What is it? And how can it save them all? For Cass and Wilbur, slaving to dig it up, there are no answers. But when two strange children from another time turn up, claiming to know all about the lost relic, their world is changed forever. Together they have six days left to find it. Six days to the end of the world… or the making of the next… A chilling fantasy adventure set in post-apocalyptic London.