Julia is a highly successful online magazine editor preparing to marry reality television star Will Slater. She comes from a wealthy but emotionally distant family. Julia is a highly organized individual who fiercely protects her meticulously curated public image. She uses perfectionism to mask deeper insecurities and a lingering resentment toward her parents for their absence during her childhood.

Will is the handsome celebrity host of a wilderness survival reality television show called "Survive the Night." He attended a prestigious boarding school where his father was the headmaster, and he is accustomed to getting what he wants. He projects a flawless, golden-boy image that charms almost everyone he meets, particularly his devoted pack of school friends.

Aoife is the composed wedding planner and co-owner of the island property known as The Folly. Originally from Dublin, she and her husband want to build a successful destination wedding business despite the island's eerie reputation and ghost stories. She projects a cool, detached professionalism while she manages the chaotic wedding event.

Hannah is Charlie's wife and a former graphic designer currently on maternity leave. She feels insecure about her post-pregnancy body and financially out of place surrounded by the wealthy wedding guests. She approaches the weekend with trepidation. She is highly observant and fiercely protective of those she cares about, and she carries a deep grief for her late sister.

Olivia is Julia's nineteen-year-old half-sister and the maid of honor. She struggles profoundly with her mental health and frequently seeks isolation to cope with her internal turmoil. She carries the weight of a recent, devastating romantic experience, making her feel alienated from her sister's picture-perfect celebration.

Johnno is Will's best man and oldest friend from their boarding school days. Unlike the rest of the groomsmen, he comes from a working-class background and struggles with career stability. He currently works at an outdoor adventure camp. He masks his insecurities by claiming to run a whiskey business, heavily relying on his lifelong connection to Will for status.

Freddy is a warm former Dublin restaurant owner who now serves as the chef for The Folly. He works alongside his wife to ensure the wedding's success. He provides a gentle, comforting presence for the high-strung wedding party and acts as a grounding force for his stressed partner.

Darcey is Aoife's brother and Freddy's childhood friend. His tragic passing in his youth had a profound impact on his family. He leaves a lasting legacy of grief that deeply affects his sister.

Alice is Hannah's late sister. She was a highly intelligent and driven woman who once aspired to a career in politics. Her tragic death years ago left a massive void in Hannah's life. Her memory heavily influences Hannah's protective nature toward other vulnerable women.

Charlie is a schoolteacher and Julia's oldest friend. When surrounded by the wealthy wedding guests, Charlie noticeably shifts his behavior. He adopts a posher accent and tries desperately to fit in with the groomsmen. This desire for social acceptance causes significant friction in his marriage, as he prioritizes the approval of the other men over his wife's comfort.

Duncan is one of Will's groomsmen and a wealthy economics professional. He is a crass individual who acts aggressively toward others. He takes pleasure in casually belittling his peers, including his own friends, to assert his dominance within the group.

Olufemi is a successful surgeon and one of Will's groomsmen. He maintains a fond view of his boarding school days despite the challenges of his youth. He actively participates in the group's rowdy traditions and displays strong loyalty to his former classmates.

Peter is an advertising professional and one of Will's groomsmen. Characterized by his party-boy lifestyle and substance use, he is highly susceptible to paranoia. He becomes easily frightened when the island's eerie atmosphere and the impending storm begin to affect the group's morale.

Ronan is Julia's self-made businessman father. He has been emotionally and financially absent from much of her life, and he recently started a new family. This creates a deep rift between him and his daughter. Despite their estrangement, he maintains a fierce, if awkwardly expressed, protective instinct toward her.

Araminta is Julia and Olivia's mother. She is a trendy woman who often centers conversations around herself. She can be overdramatic and self-absorbed, but she genuinely cares for her daughters. She maintains a particularly anxious watch over Olivia's well-being.

Angus is one of Will's groomsmen who works at his father's firm. Like the rest of the boarding school clique, he enjoys the rowdy traditions of their past and follows Will's lead during the wedding festivities.

Georgina is Duncan's wife. She attends the destination wedding on the island and casually engages in the group's conversations. She sometimes makes offhand comments about the men's boarding school history without realizing the impact of her words.

Piers is the television producer for Will's wilderness survival show. His presence at the wedding introduces professional complications for the groom, as he holds the keys to the cast's future on the program.

Mattie is the local boat captain responsible for ferrying the wedding guests to the remote island. He knows the local lore well and shares the eerie, haunted history of the island with his passengers.

Severine is Ronan's new wife, a woman close in age to Julia. Her presence at the wedding exacerbates the already awkward and tense family dynamic between Julia and her father.

Callum is Olivia's ex-boyfriend. Their breakup is the initial reason given for Olivia's deep depression and isolation during the wedding weekend.