Pale Horse (Silentium)

When Jeniffer's closest friend Marcus is murdered she is drawn into a world which tempts her to break the Silentium. Another Witch known only as The Sorori, or the Sister, is gathering power. The Sorori plans to make war on mankind and return the world to the age of Goddess worship, killing all who don't convert. To stop The Sorori Jeniffer must engage in a modern day witch-hunt but the hunt means discovering the truth of her own past and the true origins of the Silentium.