Jessalyn Thornton is a young woman from Chatham County, Georgia who was born in 1989.
In 2013, Jessalyn is about to get married to Colton Birchfield and decides to have a sleepover with her friend Addison Hammond at the abandoned Thornton Hall (where her mother's cousin Charlotte lost her life twenty years before) for a bachelorette party. At first the girls have a lot of fun, but at one point Addison loses sight of Jessalyn and hears her scream. Addison is too petrified to go looking for her friend, but luckily Jessalyn comes back to her before long. Unfortunately, the night isn't fun anymore because Jessalyn is no longer happily excited- she instead has grown sullen and orders Addison to leave her alone. Soon after, Jessalyn goes missing. The experience scares Addison so badly she runs home after alerting the Thornton clan of Jessalyn's disappearance.
Believing that Charlotte, Blackrock Island's infamous ghost, is haunting Thornton Hall and may have had something to do with the disappearance, Jessalyn's mother's cousin Wade calls Savannah Woodham to come investigate. However, Savannah is too frightened to accept the case and instead asks Nancy to help the Thorntons in her stead.
During the day, everyone searches Blackrock Island for any trace of Jessalyn. At night, Clara, Colton, Wade, and Nancy stay close to Thornton Hall in case Jessalyn comes back. Clara, her mother, thinks that perhaps Jessalyn has been kidnapped as a ransom, but there has been no note demanding money. She tells Nancy that instead of staying home, every single one of her employees volunteered to help look for her daughter. Wade believes that the ghostly Charlotte has taken Jessalyn. Colton admits that it's possible his fiancée has had second thoughts about the wedding, but says she would never put her family through this terror.
During her investigation, Nancy discovers that the marriage between Colton and Jessalyn is heavily pushed by their parents. The Birchfields want access to the Thornton fortune and Clara wants part of the Birchfields' political influence. Although Colton and Jessalyn are very good friends, they don't love each other romantically. In fact, Jessalyn hopes that they can break off their wedding so Colton will be able to pursue his true love, Lexie.
Nancy eventually finds Jessalyn hiding in a tunnel in the basement. She explains to Nancy that during the sleepover, she was found by her mother's cousin, Harper Thornton. All her life, Clara told her that Harper was insane, but Jessalyn listened to what Harper had to say because her mother always seemed so cold to her, and what Harper said made sense of her mother's behavior. Harper told Jessalyn that she needs her help in proving that Clara killed Charlotte. 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. 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.
Nancy can choose to help Jessalyn rescue Harper, but if Nancy refuses, both Jessalyn and Harper are hospitalized, Clara is never found, and Colton and Wade refuse to speak to Nancy. If the detective rescues the two, but doesn't save Clara, Jessalyn says she needs to take some time away from the family, maybe permanently, and disappears along with Wade. If Nancy saves all three women, Jessalyn takes charge of the family business and offers Wade a position on the board, tasking him with the job of keeping tabs on the company's labor force. She and Wade also track down Harper, who had vanished shortly after the fire, in order to convince her to rejoin the family. She and Colton patch up their friendship and are both relieved to call off their marriage so they can live their lives how they want.
- Jessalyn's personality is very similar to Charlotte's. Both are considered to be the "bright spots of happiness" in the Thornton family.
- According to Addison, Jessalyn always loves a good scare. She would sneak into scary movies with Addison when they were kids.
- Jessalyn used to call Clara "Chairman Mom" behind her back.
- The first time she and Colton met as children, he threw a rock at her face. She still has a little scar that can be seen when she smiles.
- "I stayed to listen. I didn't laugh. I didn't run away. I stayed, and listened to every word. Because my mother, because she's so...cold. And I believed that it might be true."
- "Colton and I were never in love. We were in a mess."