Iron Circle, by Dave Ellis

Dr. Sandra Moore, a Reader in Inorganic Chemistry at Cloxford University, is preparing for an academic conference when a simple outing to the ancient Ironblane Circle draws her into a mystery far older than the stones themselves.

At first, the signs are impossible to explain: vivid nightmares, missing hours, unnatural weather, and visions of Emily Barnett, Sandra’s great-great-grandmother, long rumored to have died at the Circle. But as the disturbances grow more dangerous, Sandra learns that the world she understands through science may be only the thinnest surface of reality.

With the help of an enigmatic caretaker, a skeptical colleague, and forces stranger than she ever imagined, Sandra must confront an ancient threat before the Earth itself is claimed. Iron Circle is a fantastical tale of ghosts, gods, time, and the perilous boundary between knowledge and belief.