How will Blake Walker and his friends defeat a woman who has served the forces of darkness for over a hundred years?

Blake Walker and his friends have been drawn into the universal war between the forces of light and darkness. On a school field trip, they encounter Millicent Andrews, a woman who has served the forces of darkness for over a hundred years. But she isn't the only threat. Ivan Kosoff, a boy from their high school, has just lost his brother because of his refusal to follow the darkness's orders. Ivan claims he wants to help Blake and the others fight the darkness, but can he be trusted? And how can they defeat someone as powerful as Millicent?