Liz Cook is a cop who was on the call (along with partner Dennis Baldwin) when Amy Kettering's young daughter, Emily, is kidnapped. Emily was kidnapped as part of a conspiracy to force Amy to kill Borden, a reporter looking to expose a group who was planning to steal a flu vaccine and sell it on the black market. While following a suspect, Liz tells Amy that Baldwin is part of the plot, and takes Baldwin's gun while holding him at gunpoint. She also removed Amy's cuffs and gave her a gun of her own, but while Amy held Baldwin at gunpoint and demanded to know Emily's whereabouts, Liz turned heel and shot Baldwin to death, revealing her role in the conspiracy.
Liz's plan was to frame Amy for Baldwin's murder, and she chased after Amy with intent on killing her. She later returned to Amy's home and grilled her mother regarding Amy's whereabouts, and later on, the evil Liz appeared at the home of politician Paula Stronin, who was later revealed as the mastermind behind the theft of the flu vaccine. After killing co-conspirator Duncan Hall, Amy battled Liz once again, with the battle ending with the villainess being handcuffed to her car and forced to reveal Emily's whereabouts: the trunk of the car. Though not shown, Liz was arrested in her role in the conspiracy.
- Sonja Bennett also played serial robber Beth on Tru Calling, and later played crazed villainess Chelsea Richmond on Motive.