For centuries, war has been brewing below the surface of New York. People known as the soulless - immortal humans with strange powers - have threatened life on the surface. The Dark Queen seeks revenge for a crime long forgotten and wants to rule the world. Eighteen-year-old Riley Stark - a new recruit in the Sentinels, a military group that protects Earth from the Underworld - thinks she's joining for the right reason. As a child, she narrowly escaped an assassination attempt on her life, and has wanted justice ever since. After Riley goes snooping through her records, she finds the terrible truth - her ancestor was Mira Stark who killed the famous Dark King, and the soulless have wanted her family's blood spilled. When Riley falls in love with a soulless boy she's been taught to hate, she realizes that she can't trust anyone - soulless or otherwise.