The Agathas' fromt cover
Carol Westmacott is the main villainess of the 2022 mystery novel The Agathas. She was introduced as the guidance counselor at Castle Cove High School who set up student Iris Adams to tutor Alice Ogilvie (the two girls being the book's co-protagonists). Carol displayed a warm personality in her introductory scene, urging Alice to get into horse-riding to combat negative emotions that had led to her running away from home the summer before the school year began.
The book's early events saw Alice's former best friend Brooke Donovan, step-daughter of school basketball coach Matt Donovan aka Paul Bradford, disappearing after a Halloween party at her ancestral castle with a search conducted by Alice, Iris, and the latter's friends, "The Zoners", eventually resulting in her water-logged corpse being found on the beach below a cliff near the castle. The girls' investigation into Brooke's death led them to discover that Matt was a philander who had been secretly dating many staff members at Castle Cove High School and that Carol had been dumped by him due to Brooke not liking her and feeling as though her late mother Victoria was being replaced.
Carol showed odd behaviour during the course of the investigation, such as arriving outside the Donovan family home with a box of Matt's belongings, claiming she was giving them back following their break-up. Eventually, evidence (including footprints from Matt's sneakers and Brooke having a head wound proven to have been caused by a trophy he owned) was gathered that led to Matt being arrested for Brooke's murder, exonerating her boyfriend, Steven Anderson, in the process. Carol continued to act in a strange fashion following the arrest with an interview she gave regarding her relationship with Matt being watched by Alice and Iris. Some time later, after an argument with Irish, Alice went to the town stables to ride her horse Snowflake.
However, when she arrived, Alice heard strange mumbling coming from one of the other stalls. It was revealed to be Carol, who was angrily ranting about Matt's arrest. This led to the revelation that not only was Matt innocent but Carol was in fact Brooke's murderer. On Halloween night, Carol had intended to throw Matt's belongings that had been left at her house off the cliff and into the sea as revenge for him dumping her. Brooke, drunk from the party, then arrived at the scene, disoriented after an argument with Steve. Carol, sensing a chance to get her approval in the hopes of Matt taking her back, approached Brooke (wearing Matt's sneakers whilst doing so), and wrapped a jacket around her.
Brooke coldly rebuffed Carol's attempts at goodwill, telling her Matt didn't love her, infuriating her and driving her to slap Brooke in anger. When Brooke tried to flee down the highway, Carol caught up to her (boasting about how her college track career had enabled her to do so) and hit her over the head with Matt's trophy. Eventually, Brooke fell over the edge of the cliff as a result of the chase, begging Carol to save her as she desperately clung to the rocks at the edge of the cliff. However, Carol had grown to despise Brooke for (in her mind) being the one thing that stood between her and Matt, leading to her completing her heel-turn by allowing Brooke to plummet to her death.
After the revelation, Carol knocked Alice out and dragged her outside, intending to run her over before escaping the town in her car. Although Alice recovered in time to avoid the murder attempt, she was unable to prevent the evil Carol from fleeing the stables, leading to a chase where Alice rode Snowflake after the psychotic villainess. Following a frantic chase, Carol crashed her car into a redwood tree, being left incapacitated as a result. Alice took her out of the burning car as she delusionally threatened to have her expelled for assaulting a teacher. Carol was then gagged with Alice's scrunchie and bound with horse reins as Alice's friends arrived on the scene after figuring out Carol was the true killer. Carol was arrested (off-screen) for Brooke's murder which was reported on the news in the book's final scene.