She was played by Laura Harris, who also portrayed Marybeth Louise Hutchinson.
Tracy was a patient of Dr. Rachel Corrigan, and she was having these vivid nightmares involving a wolf-like creature. Of course, an actual werewolf does prowl around the city on a killing spree, and Tracy's mother, Anne, actually reveals that her daughter's dreams are real. A werewolf did go after them years ago, but Anne actually shot and killed the beast, who was revealed to be Tracy's father. The revelation leads the Legacy group to believe that somehow, Tracy's father had come back and was after his wife and daughter. However, a scene shows the werewolf climbing in Tracy's bedroom window, lying down in her bed, and reverting back to its human form, which is revealed to be none other than Tracy Lasker herself.
Later on, Rachel is at the Lasker house because Anne said that Tracy was missing, but they both find her in her bedroom asleep. Late at night, while the rest of the Legacy group is outside waiting for the werewolf to appear, Rachel is alone with Tracy, who is asleep in her bed. To Rachel's shock, the evil Tracy transforms into a werewolf and rises out of her bed growling at Rachel before she lunges at Nick, who later shoots and kills her. The rest of Legacy group learns that Tracy was the werewolf after seeing her revert back to her human form.