After finding himself caught up in one of Louisiana's oldest and bloodiest family rivalries, Detective Dave Robicheaux must battle the most terrifying adversary he has ever encountered: a time-traveling superhuman assassin. The Shondell and Balangie families are longtime enemies in the New Iberia criminal underworld and show each other no mercy. Yet their youngest heirs, Johnny Shondell and Isolde Balangie, rock and roll-musician teenagers with magical voices, have fallen in love and run away after Isolde was given as a sex slave to Johnny's father. As he seeks to uncover why, Detective Dave Robicheaux gets too close to both Isolde's mother and the mistress of her father, a venomous New Orleans mafioso whose jealousy has no bounds. In retribution, he hires a mysterious assassin to go after Robicheaux and his longtime partner, Clete Purcel.