Raybould Marsh is a British secret agent in the early days of the Second World War, haunted by something strange he saw on a mission during the Spanish Civil War: a German woman with wires going into her head who looked at him as if she knew him. When the Nazis start running missions with people who have unnatural abilities - a woman who can turn invisible, a man who can walk through walls, and the woman Marsh saw in Spain who can use her knowledge of the future to twist the present - Marsh is the man who has to face them. He rallies the secret warlocks of Britain to hold the impending invasion at bay. But magic always exacts a price. Eventually, the sacrifice necessary to defeat the enemy will be as terrible as outright loss would be.