As the daughter of a rancher in 1840s Mexico, Nena knows a thing or two about monsters. Something sinister lurks near the ranch at night, something that drains men of their blood and leaves them for dead. Something that once attacked Nena nine years ago. Believing Nena dead, Nestor has been on the run from his grief ever since, moving from ranch to ranch working as a vaquero. But when the United States invades Mexico in 1846, the two are brought abruptly together on the road to war. The shock of their reunion is quickly overshadowed by the appearance of a nightmare made flesh. And unless Nena and Nestor face the future together, neither will survive to see the dawn.