Four young women - Tessa van Marter, Nisha Johns, and the Braden twins Cassie and Carrie - collectively calling themselves the Dia Tessaron after the Diatessaron, a compilation of the New Testament Gospels written in the 2nd Century, are on a campaign to root out and destroy the deranged mad followers of various Great Old Ones. One of the Great Old Ones, Nyogtha, the Thing That Should Not Be, set's its sights on the four young women. And in the end, a mysterious stranger appears, claiming to be the brother of Tessa, but Tessa has no brother.