Jack thinks he is investigating psychics and spirit mediums. A Bavarian professor hired him to research a new book. Jack soon discovers a whole new world. He learns there is a different species of human living among us. Professor Kruger calls them Homo Sapiens Obscurus. They are like us, but special powers set them apart. They have the gift of illusion, using a form of hypnosis to change their own appearance.
They can look like angels, demons, or monsters. Or they can resemble your friendly mailman, or your boss. They can go anywhere and do anything. Now the professor wants to publish a book about them. That could be dangerous. When the Others learn of his plans, they strike back.