Sergeant Voight tries to find out who is behind the murder of Jin, and e up with the unbelievable disvery and learned that Sergeant Edwin Stillwell playing a double game with the intention of getting out on the surface of the big fish along with Voight. In the meantime, all members of the intelligence depments receive death threats from an unknown group called "Shadow". At several places in Chicago in a fire, explosion, and robbery, for which "Shadow" take responsibility, bringing the city into chaos.