1925. Mary Russell and Sherlock Holmes arrive home to find a stone. The stone is inscribed with the same name that they last saw in the Tokyo garden of the future emperor of Japan. It is the first indication that the investigation they did for him a year ago might not be as complete as they had thought. In Japan there were spies; in Oxford there are dreams. In both places, there is a small, dark-haired woman, and danger . . .