The Dark Cycle (Marks)

Aidan O'Linn's childhood ended the night he saw a demon kill his mother and mark his sister, Ava, with Darkness. Since then, every three years the demons have returned to try to claim her. Living in the gritty, forgotten corners of Los Angeles, Aidan has managed to protect his sister, but he knows that even his powers to fight demons and speak dead languages won't keep her safe for much longer.

Against the backdrop of an ancient battle between the forces of Light and the forces of Darkness, Aidan struggles to control the newly awakened and enigmatic powers that seem to be his only hope for rescuing Ava, his little sister, trapped somewhere beyond the Veil. As he gravitates to Kara, the beguiling and dangerously unstable girl who helped him realize his abilities, a terrible mistake of fate is revealed that points him back toward Rebecca, whose role is becoming more critical to the battle.

The fate of humanity hangs in the balance as Aidan faces a crushing choice: give in to the demands of the forces of Darkness in order to save his sister, Ava, or fight on the side of good and risk losing her forever. With so much at stake and so little time, Aidan rushes to finish assembling a team of Lights, other teens whose special abilities are linked to his own.