Lucian, Guardian of the Underworld Gates, flees the realm of the dead with his daughter Mila—who bears the power of the River Styx—and surfaces in the mortal city of Vesper to live an ordinary life. On the streets he rescues Valerie, heir to the Ashford family, who is being hunted; to dodge an arranged marriage, she proposes a contract marriage, and the two wed. Adrian Hawthorne's family closes in: they kidnap Valerie and send Underworld envoys to kill. Mila, with her superhuman strength, shields her mother again and again, while Lucian silently erases the memories involved. Mila also hacks the enemy's bug and exposes cousin Gavin's plot to forge drug evidence and frame Valerie. At the family council, father and daughter shatter the scheme—just as Adrian arrives with gunmen to seize the docks. Meanwhile, Charon has sent Ronan into the mortal world, and their peace faces threats from both the Underworld and the mob.