San Antonio is full of secrets, and seventeen-year-old Erasmo Cruz investigates the strangest of them. After gaining renown for surviving the city's legendary Ghost Tracks, he has set up shop as a paranormal investigator. But helping exorcize other people's demons doesn't seem to relieve his own; his best friend Rat has abandoned him, his grandmother is nearing death, and his own health has taken a sudden decline.

None of these hardships can prepare Erasmo for the story his newest client brings him. Two decades after a strange ritual at a rural ranch, Bradley Erickson is being hunted by the Devil. In exchange for the life of his dreams, Bradley must surrender the blood of his child. The case hurls Erasmo into a dark web of cults, bargains, and broken pasts. Only one thing is certain: the Devil keeps his promises.