When the dead start humming with corrupted data and the city’s protective wards begin to fracture, New Orleans’ fragile peace cracks open. Nova Tran, a culpable coder turned reluctant techno-witch, discovers her mentor’s old enemies have matured into a lethal new strategy: weaponize the city’s ley lines through servers and spirits. To stop the True Krewe du Code Noir, Nova must partner with Selene Rousseau, vampire, aristocrat, and unwilling ally, and guide a ragtag group of couriers, musicians, and bookshop witches into a battle beneath the Cathedral.

As the Serpent’s Cipher adapts, choices become unbearable. Vivienne Laurent offers a bargain that could buy victory but cost the city its agency. Marcy, a saxophonist who hears the city’s pain, may be the only one who can sing the counter-frequency. Nova must decide what she’s willing to become to save what she loves—and whether a liberated city is worth losing herself for.