The blizzard ended by morning. The sky cleared to a pale blue as dawn glided over the hills east of Edo, leaving the city serene under a mantle of fresh, sparkling snow. Cranes flew over the rise where Edo Castle perched. The great fortress wore white frosting atop its walls and guard towers. In the innermost precinct of the castle stood the palace. Dark cypress beams gridded the white plaster walls of the low, interconnected buildings; gold dragons crowned the peaks of its tile roofs. In the garden, boulders and shrubs were smooth white mounds. Ice glazed a pond surrounded by trees whose bare branches spread lacy black patterns against the brightening sky. The snow on the lawn and gravel paths was pristine, undisturbed by footprints. The garden appeared deserted, but appearances were deceiving.

Under a large pine tree, in a shelter formed by its spreading boughs, three samurai crouched. Sano Ichiro, the shogun’s sosakan-sama-Most Honorable Investigator of Events, Situations, and People-huddled with his two top detectives, Marume and Fukida. Although they’d covered the ground with a quilt and they wore hats, gloves, fleece-lined boots, and layers of thick, padded clothing, they were shivering. They’d been here all night, and their shelter was cold enough that they could see their breath. Sano flexed his numb fingers and toes in an attempt to ward off frostbite, as he and his men watched the palace through gaps between the bristly, resin-scented pine sprigs.