A protagonist from a working-class background, ambitious and diligent, she aspires to a better life for her and her daughter Lucy, while overcoming traumatic experiences and loss.

A protagonist with a talent for puzzle-solving, she works at BP, rising in resilience and autonomy despite an oppressive upbringing and working in challenging environments.

A friendly, red-haired man at BP known for his charm and negative traits that are revealed over time; he has interactions with Osla and concerns surrounding secrecy.

Mab’s first husband, a World War I veteran and poet, known for his soft-spoken nature, literary expression, and supportive marriage to Mab.

A BP codebreaker and love interest to Beth, of Arab, Maltese, and Egyptian descent, who deals with racism while balancing his sense of duty and integrity.

Beth’s friend and mentor at BP, depicted as an eccentric yet heroic codebreaker, who becomes a father figure to Beth.

Osla’s longtime boyfriend, known for his royal honor and restraint in their relationship, ultimately influencing Osla’s character journey.

Beth’s parents, particularly her domineering mother Mrs. Finch, with traditional views and disapproval of Beth’s work and social life.