When two operatives go dark in Tampa, chasing the trail of an oligarch with ties to the demonic underworld, Vigilant Lock—the nation’s first and last line of defense against occult attack—sends their best to the rescue: Harmony Black, a troubled investigator and an elemental witch with a keen but tangled mind; and her partner Jessie Temple, the daughter of a supernatural slasher and the inheritor of her father’s powers. The trail of clues leads them to the doorstep of Judah Cranston, a wealthy scientist with dark secrets and a darker agenda. Toss in an alluring marine biologist with eyes for Harmony, and a pair of demon-blooded troubleshooters on a hunt of their own, and Tampa Bay is heating up fast. As the mission takes Harmony and Jessie from the sun-drenched Florida coast to a gloomy New England fishing town steeped in forgotten history, they find themselves up against a threat far greater—and more otherworldly—than they ever expected.