Ever since their mother died and their father went missing, Dorie and Bram Violet have lived alone, quietly making a life for themselves in the Fens of the seventeenth century. But unexpected changes to the landscape and waterways threaten to cut them off from their livelihood and from one another.
 
As the two search for answers, they come face to face with the folk monsters of the Fens, the rich men and their prisoners who are draining the land of water, and the local resistance movement determined to get in their way: the fearsome Fen Tigers.
 
Yet Dorie and Bram have very different ideas about how far they’re willing to go to protect their land, and when Bram joins up with the resistance, Dorie must leave home and push himself to his limits to keep his brother safe from harm.