Anathema : Book 1, The Evil That Men Do

How far will one woman go for the salvation of her beloved? Mercy Barlowe's love for Sarah brings down Hell when her puritanical father discovers them together - and has his own daughter burnt at the stake. But death is not the end. A monstrous cult of shapeshifters steal Sarah's soul as part of its twisted plans to resurrect an ancient evil. To defeat them, Mercy must take on a new form...She must become a werewolf!