All readers know that good novels draw us into other worlds. I cannot think of another, however, which so alarmed me as this one, just as events alarmed and frightened its central character.

She is Okatsu, a young woman from the samurai Satsuma Clan in mid-19th-century Japan. The country has been ruled by the shogunate, a military caste, since the early 17th century; the emperors were remote figures until their restoration to power in 1868.