F.B.I. criminal profiler Diana Mancuso doesn't do field work anymore. Not since a tragic mistake that cost innocent lives. But when notorious serial killer Luther Vayne escapes from prison and resumes his campaign of brutal murders, the Bureau convinces her to take one last case.

To catch him, she must understand him. She must delve into the arcana that fuels his madness, risking her life and her sanity to follow his twisted path. The trail plunges her into a shadowy world of occult rituals and unspeakable horrors, leading to a secret cabal operating at the highest levels—and a plot to summon the darkest of all powers, to bring forth an evil that does not belong in our world—to enact the Rites of Azathoth.