Ellis is one of the main members of the Sterling Point group, Joe's son, and one of Petal's and Annie's primary romantic interests. He is quiet, observant, dryly funny, loyal, and more emotionally perceptive than he first appears. He has a calm presence and tends to listen rather than immediately speak. Unlike the more openly flirtatious Rory, Ellis is subtle. He tends to show affection through attention, time, and small acts rather than dramatic declarations. He knows the island and its people well, which makes him someone Annie can naturally rely on while she is still trying to understand this new world. Ellis's role in the story is both romantic and connected to the larger mystery. His growing relationship with Annie gives her a personal connection to Sterling Point beyond her family history while still being connected to his history with petal. At the same time, his father Joe has important ties to Goldie and the secrets surrounding Ramona's past, meaning Ellis's family is also connected to the mystery.

She is intelligent, curious, ambitious, anxious, and emotionally intense. Annie normally likes having a plan and knowing where her life is going, so discovering that her family has hidden an entire part of her history from her completely disrupts her sense of identity. Annie and her twin brother Connor inherit Sterling Point from their estranged grandfather, Gordon, whom they never knew. After discovering that their adoptive father Steven hid Gordon's letters from them, Annie becomes determined to find out why. She travels to the island and discovers that her family history is far more complicated than she ever imagined. Annie's role in the story is to uncover the truth. Her arrival sets everything in motion. She discovers Ramona, her connection to Goldie, and the secrets surrounding Gordon, Steven, and the island. At first, Annie only wants answers, but she gradually develops an emotional attachment to Sterling Point. she is beginning to see the island as more than an inheritance—it may be the first place where she truly understands who she is and where she belongs.

Rory is charismatic, confident, charming, and openly flirtatious. He is one of petals and Annie's other romantic interests and creates a contrast with Ellis. While Ellis is quiet and subtle, Rory is much more direct about his attraction. Rory's role is to create romantic tension and pull both Annie and petal further into the island's social world. both Rory and Ellis are interested in them, creating an emerging love triangle. Rory represents the more immediate and obvious romantic possibility, while Ellis represents the slower, deeper connection. With petal he is more open to his faults and honest about his problems and passion including piano.

She is independent, blunt, stubborn, guarded, and deeply attached to the island. Unlike Annie, Ramona grew up there, so Sterling Point is not a mystery or inheritance to her—it is home. When Annie suddenly arrives and reveals information about Goldie and their shared family connection, Ramona's entire understanding of her life is disrupted. Her first reaction is defensive because she does not know Annie and sees her as someone invading the home she has always known. Ramona's role in the story is extremely important because she is at the center of the family's hidden history. Through her, Annie learns that there are people connected to her mother and grandfather that she never knew existed. Ramona also becomes Annie's newly discovered sister, creating one of the main emotional relationships of the story. Their relationship begins with confusion and hostility but slowly develops into something more protective and genuine. She also represents the emotional heart of the conflict surrounding Sterling Point. When Connor wants to sell the island, Ramona has the most personal reason to refuse. Losing Sterling Point would mean losing her home, memories, and connection to Gordon.

Oona is part of the main social group and one of Ramona's closest friends. She is expressive, playful, warm, and socially confident. Oona helps create the lively social world Annie enters after arriving on the island. Her most important role is her relationship with Ramona. Their connection is emotionally complicated, and Ramona's reaction to Oona's romantic life suggests that her feelings may be more than friendship. Oona represents a part of Ramona's life that existed long before Annie arrived.