Brenda hatches a plan with a man named Paul Fox to obtain the wealth of Karen and Christie (the protagonist) Cromwell. Paul marries Karen, but shortly after, Christie begins to grow suspicious of him; even to the point where she fears that he may be trying to kill her mother.
Christie begins to trail Paul in secret, eventually learning that he has been cheating on Karen with Brenda. Her sleuthing eventually leads her to the home of Lacey Bohle; a man who Brenda previously introduced to Paul as her brother. Christie manages to snap a Polaroid of Brenda and Paul having sex, but is caught in the act. While hiding inside of the house, Christie overhears Brenda and Lacey talking. Here, she learns not only that they plan to kill her and her mother for their money, but that the two are in fact not siblings, but husband and wife. Lacey is furious with jealousy, accusing Brenda of greatly enjoying her sexual escapades with Paul, but the villainess insists that it is all part of the plan to eventually blackmail him.
Later, Christie shows her mother the Polaroid as proof of Paul's infidelity, leaving the stepfather to execute a last resort. That night, he, Brenda, and Lacey invade the Cromwell home and rough Christie and Karen up before tossing them into the cellar. The trio state that they plan to murder the mother and daughter around 2 A.M. and make it look like a burglary. All seems lost, but Christie refuses to give up. She hatches several tricks of her own, which cause the villainous trio headaches, as well as physical injuries, at every turn. Ultimately, Brenda falls into one of her deadly traps. After Christie takes out the power for the second time, Brenda goes down to the cellar to check the fuse box. Due to the surrounding darkness, she fails to notice the puddle of water beneath said box, and is electrocuted. Paul and Lacey are then killed sometime after.