Nan is Archie Christie's mistress, a calculated woman who has seamlessly integrated herself into his life. Originally a carefree girl who spent idyllic summers in Ireland, she harbors painful memories from her past that drive her current actions. She possesses a keen ability to read the psychology of those around her, using this insight to carefully pursue her personal goals.

Archie is Agatha's wealthy husband, a man who strongly dislikes emotional discomfort and prioritizes his own happiness. He oscillates between his marriage and his affair, seeking total control over his environment. His self-centered nature often puts him at odds with the police investigating his wife's disappearance.

Agatha is a celebrated mystery novelist reeling from the sudden collapse of her marriage. While she is practical and highly independent in her professional life, she views her primary identity as Archie's wife. Her mysterious disappearance sparks a nationwide search, forcing her to reconsider her dependence on her marriage.

Finbarr is an Irish man who captured Nan's heart during their youth. Once known for his boundless positivity and simple view of happiness, his time as a soldier in the war has quieted his demeanor. He remains deeply connected to Nan and travels to England, where he becomes entangled in the ongoing mystery.

Inspector Chilton is a recently retired police officer recalled to help search for Agatha Christie. He carries physical and emotional wounds from the war, including a damaged arm, but remains an empathetic and observant investigator. He frequently considers the moral weight of his duties while trying to piece together the truth.

A young woman who forms a close bond with Nan during a difficult period in their youth. She carries profound trauma from her treatment at the hands of authority figures. She eventually travels to America but remains connected to her past, crossing paths with the others at the Harrogate hotel.

A woman who initially presents herself as a lenient and kind presence at the convent. She dreams of having a traditional family, a desire that heavily influences her actions. She later stays at the Harrogate hotel as a newlywed, proudly displaying her marriage to the other guests.

Teddy is Archie and Agatha's young daughter. She spends much of her time separated from her parents while they travel, forming attachments to the toys they leave behind. She naturally draws affection from strangers and becomes a focal point of Nan's attention.

Miss Armstrong is an outgoing, romantically inclined guest at the Harrogate hotel. She enjoys observing the other guests and frequently speculates about their relationships, bringing a lighter, gossipy energy to the tense environment.

Mrs. Leech is the Caribbean proprietress of the hotel in Harrogate. She manages the establishment alongside her husband and observes the unusual activities of the guests staying during the investigation.

Constable Thompson is the police chief leading the official investigation into Agatha's disappearance. He grows increasingly suspicious of Archie's evasive behavior and frequently clashes with him over the search efforts.

Honoria is Agatha's devoted maid. She attempts to comfort her employer following Archie's sudden departure and is the one who officially notifies the family when Agatha goes missing.

Colleen is Nan's beautiful older sister. Her tragic experiences during the war deeply affect her family, serving as a cautionary tale that shapes her mother's actions and Nan's perspective on survival.