Liz Cook is a cop who was on the call (along with partner Dennis Baldwin) when Amy Franklin’s young daughter, Emily, is kidnapped. Her abduction was part of a conspiracy to force Amy to kill Ed Borden, a reporter looking to expose a group who had stolen a flu vaccine and planned to sell it on the black market; if Amy didn’t comply, Emily would die.
While following a suspect, Liz ordered Dennis out of her car and falsely informed Amy that Baldwin was part of the plot. She took Baldwin's gun while holding him at gunpoint, removed Amy's handcuffs, and gave her a gun of her own, which Amy pointed at Dennis while demanding to know Emily's whereabouts. At that moment, Liz revealed herself as a villainess by shooting Baldwin in his heart, which led to his death less than a minute after the bullet was fired.
Liz's plan was to frame Amy for Baldwin's murder, and she chased after the protagonist, intent on killing her. She later returned to Amy's home and asked her mother for her daughter’s whereabouts. Later on, the evil Liz was seen on the porch of the home of politician Paula Stronin, who was revealed to be the true mastermind behind the theft of the flu vaccine; her motive for orchestrating the conspiracy was to pay off her debts. After killing co-conspirator Duncan Hall (Emily’s kidnapper and also the film’s tertiary villain), Amy held Liz at gunpoint and instructed her to exit her car. After the villainess was quickly handcuffed to her own car, Amy forced Liz to reveal Emily's new whereabouts: the car’s trunk. Though not shown, Liz was most likely arrested for her role in the conspiracy.
- Sonja Bennett also played serial robber Beth on Tru Calling, and later played crazed villainess Chelsea Richmond on Motive.