When Clara was very young, her mother Rosalie became very sick. Clara begged her to reveal the identity of her father, afraid of being left all alone, but Rosalie took the secret to her grave. Clara then went to live with her Aunt Marianna, Uncle Roger, and cousins Charlotte and Harper. Although the girls were so close everyone thought they were sisters, Clara was always uncertain about her place in the family and was worried that she might lose it. Despite these fears, she spent many happy years with her cousins' family.
Unfortunately, tragedy struck eleven years later when Marianna and Roger died together in a plane crash, leaving Charlotte as the head of the Thornton agricultural company. Perhaps thinking of her own parents' untimely demise, Charlotte soon created a will that left everything to Clara in the event of her death. However, eventually something made Charlotte change her mind and revise her will. Somehow, Clara found out that Charlotte cut her out of the will, leaving everything to Harper instead. Clara was terrified that being cut out of the will meant that she was cut out of the family as a whole, and she couldn't bear the thought of being without a family again. Scared and vengeful, she grew angry and tried to frighten Charlotte by starting a small fire, but it quickly got out of control and ended up killing her. Wracked with guilt and grief, a heartbroken Clara sat at Charlotte's grave every night for a year.
Clara's daughter Jessalyn is about to be married to Colton Birchfield and holds a small bachelorette party with her best friend Addison Hammond at the now-abandoned Thornton Hall. However, Jessalyn mysteriously goes missing in the early hours of the morning. Clara immediately travels to the manor to search for her daughter, even letting Wade call Savannah Woodham, a paranormal expert, just in case Jessalyn's dissapearance is supernatural. However, Savannah is simply too frightened to accept the case and instead turns it over to Nancy Drew.
During the investigation, Nancy discovers that Harper was devastated by her sister Charlotte's death and had "a violent outburst" at the funeral, culminating in her arrest. Harper was convinced that Clara had stolen a part of Charlotte's locket and confronted her, eventually becoming so upset she pushed Clara off the widow's walk. By the time Clara got out of the hospital, Harper was nowhere to be found. Under the shadows of Charlotte's death and Harper's running away, the family business passed on to Clara.
If Nancy asks Clara about Harper's commitment to a sanitarium, Clara tells her that is was a boarding school; Harper was just "theatrical" about it. Harper on the other hand calls her a revisionist.
By overhearing both Colton's and Clara's phone conversations, Nancy learns that Colton's parents paid his girlfriend Lexie to dump him so that they and Clara could arrange a marriage between him and Jessalyn. The Birchfields want to have access to the Thornton fortune, and Clara would have some of the Birchfields' political influence. Clara is very pushy about the wedding, making sure that she is consulted at every detail, from what kind of groomsmen Colton can have to what kind of table cards will be used. She wants the wedding to be a grand affair with fancy food and a large audience, an official uniting of the powerful Thornton and Birchfield families. Colton and Jessalyn, however, do not appreciate her meddling.Nor does Wade. Nancy learns from him that he was sent to jail for a year because he broke into one of the Thornton factories. He had heard that the workers were being mistreated, and when he saw that they were locked inside the factory, he was furious and took it out on some of its equipment. Clara claims she pressed charges in an attempt to get him to learn his lesson, because he did break the law and scared the workers half to death. But Wade contradicts that she would visit him in jail just to laugh at him through the glass.
When Nancy finally finds Jessalyn, she reveals that Harper found her during her bachelorette party. Clara had always told her daughter that Harper was crazy and to call the police if she ever saw her, but instead she listened to what Harper had to say. Harper asked for her help in proving that Clara killed Charlotte, a dark secret that Jessalyn believed could be true because her mother always seemed so cold. If Clara truly had killed Charlotte, it would explain that cold behavior.
Jessalyn and Harper were trying to frighten Clara by dressing up as Charlotte in order to scare her away from her briefcase, where she keeps a necklace that belonged to Charlotte. The necklace, an heirloom from their civil-war-spy ancestor, contains a clue to opening a safe but will destroy its contents if opened incorrectly. Nevertheless, Nancy manages to swipe the necklace and open its locket, revealing not only the safe clue but also a message about how Clara can't be trusted. Jessalyn goes to confront her mother herself while Nancy opens the safe, which turns out to contain Charlotte's will. Though originally it stated that everything was to be Clara's in the event of Charlotte's death, she had revised it the day before she died so that Harper was to receive everything instead of Clara. After Nancy reads through the will, she notices that Thornton Hall has caught on fire.
If Nancy chooses not to rescue Clara, she comments in one of her letters that a resident of the town said that she saw two ghostly images dance like smoke up from Thornton Hall.
If Nancy does choose to save Clara, she'll find her panicking in Charlotte's room. She doesn't seem able to leave, saying that she deserves to die. The hallway is too overcome with flames to get through safely, but Nancy manages to open a secret passageway to get her and Clara out. With Nancy's encouragement, Clara agrees to leave. Clara confesses everything to Jessalyn, who comments that it's the first time she saw the "true Clara". With Clara's blessing, Jessalyn takes charge of the company.
- Clara often calls her daughter "Jessie".
- "My momma was a good woman, but dang if she didn't scare me half to death with a regularity."
- "Jessie's a gem. Any man would be lucky to get the time of day from her."
- ''I can't believe I'm praying for a ransom note to show up.''
- ''They had their rows and romantic dinners same as any couple.''