Martha is a clever, sensitive writer who struggles with a severe, unnamed mental illness that first manifested when she was seventeen. She works various writing jobs, including at *Vogue* and *World of Interiors*, but struggles to maintain a stable career. She frequently feels isolated from those around her and experiences deep-seated fears about motherhood and her own identity. Her internal battles often cause her to push away the people she loves the most.

Patrick is an intensive care specialist who has been a constant presence in Martha's life since childhood. After losing his mother at a young age and experiencing a distant relationship with his father, he finds a surrogate family in Martha's relatives. He is patient, deeply devoted, and often absorbs the emotional turbulence of Martha's condition.

Ingrid is Martha's younger sister, born just fifteen months after her. Strikingly similar to Martha in physical appearance, Ingrid leads a very different life, focusing on raising her young children and managing a busy household. She is outspoken, practical, and fiercely loyal to her sister, often acting as Martha's primary emotional anchor.

Fergus is Martha and Ingrid's father, a poet who never quite achieved the literary success he initially promised. He is a gentle, attentive parent who stays by Martha's side during her earliest mental health episodes. He shares a creative connection with his older daughter, teaching her alphabet sentence games to calm her mind.

Celia is Martha and Ingrid's mother, a sculptor who creates art from repurposed materials. She prefers being the center of attention over domestic duties and struggles with alcohol, often embarrassing her daughters. Her dismissive attitude toward Martha's mental health creates a deep rift between them.

Winsome is Celia's wealthy older sister and the financial backbone of Martha's family. Living in a large townhouse in Belgravia, she provides the stability and traditional family environment that Celia cannot. She is an exceptionally skilled pianist and a quiet but observant caretaker who steps in to support her nieces.

Peregrine is the eccentric publisher of *World of Interiors* and becomes a significant mentor to Martha. Having experienced his own severe personal crises, he recognizes Martha's struggles and offers her both professional opportunities and deep, non-judgmental friendship. He frequently acts as a protective surrogate father figure.

Jonathan is an art broker and Martha's first husband. Charming on the surface, he holds deeply problematic and dismissive views about mental illness, telling Martha that affected individuals should simply toughen up. He pushes for a traditional life and children without fully understanding or accepting his wife's condition.

Nicholas is Winsome and Rowland's adopted oldest son, the same age as Martha. He struggles with his own mental health and substance use issues, leading him to bond closely with Martha during a period when they both work at an organic supermarket and take long walks together.

Oliver is Winsome and Rowland's middle child. He is the initial link between Patrick and the family, bringing Patrick home for the holidays when Patrick's father forgets to buy him a ticket. He pays close attention to the family dynamics and the relationships forming around him.

Jessamine is the youngest child of Winsome and Rowland. She grows up alongside Martha, Ingrid, and Patrick during their shared family Christmases in Belgravia.

Rowland is Winsome's wealthy husband. He provides the financial stability that supports not only his own family but also his sister-in-law's household. He can be insensitive and blunt, particularly regarding class and background, though he is ultimately a stable family presence.

Hamish is Ingrid's husband. He shares the demanding responsibilities of raising multiple young children, though Ingrid frequently vents to Martha about his lack of help around the house.

Robert is a psychiatrist married to an administrator at Patrick's hospital. He listens carefully to Martha's long medical history and provides her with an accurate, unnamed diagnosis and effective medication, completely changing her understanding of her condition.