Beacon Hills' community becomes laced with demons who are wanting something in particular and the only one who seems to know what they're doing is Stiles Stilinski's sister Addison. It seems the innocent little one isn't as clean as everyone though and only big, bad Derek Hale is willing to give her the time to explain. The King of Hell wants the Eclipse Child, a special person that he can weaponize to end the world. It's known to run in the blood of the Stilinski's maternal line, but the only problem is that neither side of the battle knows which twin is the right one. The King is willing to shed blood to obtain his prize, but the wolves and hunters of Beacon Hills are willing to do just the same to fight him off and take their town back.

Tessa Young is an 18 year old college student with a simple life, excellent grades, and a sweet boyfriend. She always has things planned out ahead of time, until she meets a rude boy named Hardin, with too many tattoos and piercings who shatters her plans.