 In the two-part season final, Sam, Bailey, Grace, and Nathan are taunted by a diabolical female serial killer who prefers to use a variety of exotic poisonous animals, (tree frogs, spiders, snakes, etc.) to kill her victims, while providing her pursuers with cryptic clues to her next murder. Meanwhile, John, now back working for the Atlanta police, arrests Francis during a drug raid and tries to talk some sense into her. A frustrated Bailey is further irritated by the arrival of a sexy private investigator, named Christine Logan, who tries to aid the VCTF, but it s the unit s chief nemesis, a jealous Jack of All Trades, who ironically can help the most when he sends fax messages to Sam of clues to the killer s identity. Also, Bailey asks Cooper to replace John on the team while Brubaker decides on a transfer for himself. Sam figures out the identity of the so-called  venom killer  as Kathryn Poole when a victim, suffering from sea wasp jellyfish stings, disappears from the hospital and it was Kathryn impersonating a victim. John and Cooper travel to Arkansas to investigate Kathryn s origins for her murderous lifestyle. Bailey takes drastic measures to curb the carousing Francis by deciding to send to a boarding school, in which she shoots him with his own gun. John debates the future of his intimate relationship with Angel and they both agree to split up. After a few taunts, Jack strikes again, first by framing the FBI and VCTF by impersonating an agent and beating up a few suspects, and then abducts both Sam and the  venom killer  Kathryn Poole, and taunts the VCTF by filming it on an Internet web site.