Unbound (Unbound #4)

Marna introduces Lucas to two other players: Jordan and her brother, Casper. Jordan, an amateur hacker, thinks she can geo-locate X so they can discover his true identity and stop him in the real world, but first they need to find him inside the game... Meanwhile, time is running out as X is becoming more sophisticated in his killing. And soon the group will learn something terrifying that they never saw coming.