Sophie is a 39-year-old single woman living in Sydney who worries about running out of time to start a family. She possesses a highly romantic worldview shaped by her parents' successful marriage and her love of Regency novels. Working a job she finds unchallenging, she leaps at the opportunity to inherit a house on Scribbly Gum Island, relishing the chance to reinvent her life and integrate into a large family structure. She suffers from a chronic physical blushing condition that occasionally causes her social embarrassment.

Connie is the recently deceased matriarch of the Scribbly Gum Island family whose death initiates the novel's main events. Growing up in poverty during the Great Depression, she took charge of her family following her mother's death and her father's struggles with war trauma. She is a clever entrepreneur who built a thriving tourist business centered around the Munro Baby Mystery, maintaining strict control over the narrative and her family's financial security for decades.

Grace is a successful children's book author and illustrator who recently gave birth to her first child. Outwardly, she appears to have an idyllic life with a loving husband and a beautiful home under construction in the Blue Mountains. Internally, she battles severe social anxiety and overwhelming postpartum depression, hiding her intrusive thoughts from her family while struggling to bond with her infant son.

Margie is a dedicated wife and mother who quietly manages the Scribbly Gum Island family business and cares for her elderly relatives. She is frequently overlooked and unappreciated by her family, particularly her husband, who routinely undermines her self-esteem with cruel jokes about her weight. Seeking personal improvement and an identity beyond her caregiving duties, she begins a strict diet and exercise regimen.

Ron is Margie's husband, a self-centered man who views himself as an essential handyman for the island's women while harboring deeply misogynistic attitudes. He routinely belittles his wife, making cruel jokes about her appearance while completely ignoring her essential contributions to their family and business. He prefers the company of male peers and resents his daughter's feminist viewpoints.

Thomas is Sophie's methodical, serious ex-boyfriend who has since married and started a family of his own. He grew up on Scribbly Gum Island and maintains close ties to his relatives there. Despite his happy outward appearance with his new wife, his past relationship with Sophie remains a point of tension and conversation within his family circle.

Veronika is Thomas's sister and a fiercely protective friend to Sophie. She possesses a combative personality and harbors deep resentment over being passed over in her great-aunt's will. Determined and inquisitive, she takes a strong interest in solving the island's historical mystery to capitalize on its potential.

Callum is Grace's extroverted, loving husband who works as a high school music teacher. He embraces fatherhood with natural ease but struggles to understand the true depth of his wife's emotional distance and depression. His friendly, outgoing nature occasionally blinds him to the severity of the domestic issues unfolding in his home.

Rose is Connie's younger sister and the last surviving member of her immediate generation. She navigates old age and intense physical pain while guarding profound secrets about her family's past and the island's famous mystery. She relied heavily on her sister's guidance throughout her life and shares a complex, interdependent bond with the other elderly island residents.

Enigma is the famous "Munro Baby" whose purported abandonment in 1932 drives the island's tourism industry. Having grown up surrounded by adoring parental figures, she deeply enjoys the attention and minor celebrity status her unique origin story provides. She is highly protective of her status and fears any investigation that might disrupt her comfortable position as the center of the island's lore.

Laura is Grace's emotionally detached mother who frequently travels abroad rather than participating in her family's daily life. She maintains a strained, distant relationship with her daughter, having employed harsh disciplinary tactics like the silent treatment during Grace's childhood. She largely avoids the intense family dynamics on Scribbly Gum Island.

Ian is a handsome, professional lawyer who handles Connie's estate and the specific stipulations of her will. He quickly takes an interest in Sophie, presenting himself as a viable candidate for the mystery suitor Connie intended for her to meet.

Rick is the outdoorsy, ruggedly handsome gardener who maintains the island's grounds. Like Ian, he pursues a relationship with Sophie, complicating her romantic prospects and adding to her confusion about Connie's final wishes.

Eddie is Sophie's childhood friend who shared her experience of being ostracized at school due to uncontrollable physical tics. They share a deep foundational bond based on mutual understanding and shared history, representing a comfortable, familiar presence in her life.

An attendee at the weight-loss group whom Margie privately nicknames "Rotund Ron" to distinguish him from her husband. He treats Margie with genuine interest and respect, inviting her to embark on a shared fitness project that greatly boosts her self-esteem and provides her with a secret source of joy away from her demanding family.

Jimmy is a young journalist who travels to Scribbly Gum Island during the Great Depression to cover the disappearance of the Munro couple. He is immediately captivated by both the mystery and the fiercely independent Connie, eventually integrating into the family structure.

Jake is Grace and Callum's newborn son. His arrival completely alters his parents' lives, sparking his father's enthusiastic embrace of parenthood while unwittingly triggering his mother's profound depression and sense of inadequacy.

Deborah is Thomas's current wife and the mother of their daughter, Lily. She presents an image of maternal bliss that inadvertently exacerbates Grace's feelings of inadequacy regarding motherhood. She remains somewhat insecure about her husband's past with Sophie.

Audrey is a fellow student at a class called "Boxercise for the Broken Hearted." She develops an immediate chemistry with Veronika, providing her with a positive new connection away from the intense family drama of Scribbly Gum Island.

Hans is Sophie's supportive father. He and his wife share an idyllic, deeply romantic marriage that serves as the benchmark for their daughter's high expectations regarding love and partnership.

Gretel is Sophie's mother, who loves recounting the precise details of how she met her husband. She maintains a close, loving relationship with her only child and fully supports her unconventional island inheritance.

Lily is the young daughter of Thomas and Deborah. Her presence serves as a reminder to the other characters of the demands and expectations surrounding raising young children.

Alice is the legendary subject of the Scribbly Gum Island mystery, a woman who purportedly vanished from her home in 1932, leaving behind a boiling kettle, a warm cake, and her infant daughter.

Jack is the second half of the famous island mystery, a man who supposedly disappeared alongside his wife during the Great Depression, sparking decades of tourism and speculation.