In 1648, the coldest year in living memory, Mercy Bennington and her neighbours struggle to rebuild their lives after the disastrous man-made flood, but the mysterious speculators are still bent on seizing their lands. The local magnate promises to help, but does nothing. Mercy's brother Tom, crippled in the earlier attacks on the Fens, returns to Gray's Inn in London, but his legal studies are not his only goal. Somewhere in London there must exist a copy of the ancient charter granting ownership of the common land to the fenlanders, provided that Tom can find it before his enemies have the chance to kill him.