Daisy is a 29-year-old woman born with a rare heart condition that severely limited her childhood experiences and life expectancy. She works as a volunteer at a care home and often dresses in clothes that make her appear much younger than her actual age. As the youngest of the Darker sisters, she feels isolated and ignored by her family due to an undisclosed past incident, observing their interactions largely from the periphery.

Beatrice, affectionately known as Nana, is the wealthy matriarch of the Darker family who lives on Seaglass, an isolated Cornish tidal island. She is a successful author famous for writing the children's book *Daisy Darker's Little Secret*. Believing a fortune teller's prophecy that she will die at age 80, she gathers her estranged, financially eager family for a final Halloween birthday celebration.

Frank is Beatrice's son and the father of the three Darker sisters. He works as a conductor for a touring orchestra, a career that provides little financial stability and historically kept him away from his family. He relies heavily on his mother's financial handouts and maintains a tense, distant dynamic with his ex-wife and children.

Nancy is Frank's ex-wife and the mother of Rose, Lily, and Daisy. Modeled somewhat after Audrey Hepburn in her youth, she maintains a vain and glamorous demeanor while living off her divorce settlement. She has a deep passion for botany and wildflowers, which inspired the names of her daughters, though she fails to nurture her children the way she tends to her plants.

Lily is the middle Darker sister and the clear favorite of their mother, Nancy. She shares her mother's vanity and has remained unemployed since becoming pregnant as a teenager. Lily frequently directs cruelty toward her younger sister Daisy and maintains an inconsistent, often harsh approach to parenting her own daughter.

Rose is the eldest of the Darker sisters. Known for her intelligence and beauty, she runs her own struggling veterinary practice, frequently offering her services for free to animals in need. She acts as the most capable and practical member of the sibling trio, often taking charge during family emergencies.

Trixie is Lily's fifteen-year-old daughter. Unlike her mother and grandmother, she is bookish, polite, and displays a quiet intelligence. She often bears the brunt of her mother's criticism regarding her appearance and reading habits, finding solace in quiet activities and writing poetry.

Conor is a BBC crime correspondent and a childhood fixture at Seaglass. As a young boy suffering from abuse, Beatrice took him under her wing, integrating him into the family circle. He holds a complicated position within the household, having been the object of affection for all three Darker sisters during their youth.

Mr. Kennedy is Conor's father who lived in a coastal cottage near Seaglass. Following the death of his wife, he struggled heavily with alcohol addiction and became physically abusive, leading Beatrice to intervene and eventually fund his rehabilitation. He periodically worked in the Seaglass gardens.

An unnamed literary agent who handles Beatrice's successful publishing career. During a past visit to Seaglass, he encourages a young Daisy to write her life story, gifting her his business card and a silver pen.

Poppins is Beatrice's elderly Old English Sheepdog. The loyal pet is a constant companion to the matriarch on the isolated tidal island and occasionally acts erratically around the old Victorian mansion.