A seventeen-year-old Texan from the wrong side of the tracks starts a supernatural detective agency—this is Fear Street for a diverse America. Erasmo Cruz is from the wrong side of the tracks. His dad was a junkie who overdosed. His mom chose to run off rather than raise him. His only passion is the supernatural and his only family is his grandmother, whose aches and pains, he soon learns, aren’t just from old age but cancer. Desperate to help his grandmother pay for treatment, Erasmo sets up shop as a detective. But he won’t be investigating burglaries or missing pets. Instead, Erasmo sets up San Antonio’s first supernatural detective agency. From hauntings to exorcisms, he soon finds that San Antonio is a much scarier place than even he knew.

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 the Devil keeps his promises.