A murderer's shooting spree in Central Park prompts Briscoe and his new partner, Detective Eddie Green, to trace the murder weapon's origination; McCoy makes it his mission to punish the killer and the gun manufacturer.

The wife of an attorney with many disgruntled clients is killed but the detectives believe that he was the intended target as he was willing to reveal information despite confidentially agreements. As the investigation continues, his tumultuous love life is exposed and the prosecutors are suspicious of his desire to return to the courtroom.

The investigation into the carjacking of a vehicle containing vials of a deadly virus leads the detectives on a search for the first person infected with the virus and a biochemist whose sinister motivations were driven by passion.