A wealthy, dark-haired debutante who is desperate to prove she is more than a silly socialite. Fluent in German, she transitions from drilling metal sheets in an airplane factory to a secretarial and translation role at Bletchley Park. She uses humor to mask her insecurities and seeks a place where she truly belongs.

A tall, ambitious young woman from an impoverished background. She aims to elevate her social station and provide a secure future for her young daughter. At Bletchley Park, she operates the noisy, physically demanding bombe machines used to break Enigma cipher keys.

A socially awkward, intensely analytical local girl. She possesses an extraordinary talent for solving complex crosswords and recognizing patterns. Recruited into the Bletchley Park cryptanalysis section, she finally finds an outlet for her mathematical mind while seeking independence from her oppressive home life.

A charming, red-haired Bletchley Park employee who organizes social events for the staff. He runs the Mad Hatters book club and provides a welcoming presence for the new recruits, though his casual banter sometimes reveals underlying prejudices.

A Cambridge-educated codebreaker of Maltese, Arab, and Egyptian descent. He frequently faces racist remarks and civilian hostility for his apparent failure to enlist, unable to reveal his crucial, top-secret intelligence work.

A middle-aged World War I veteran and poet employed at the Foreign Office. He suffers from severe post-traumatic stress and finds expressing himself through the written word easier than verbal conversation.

A highly eccentric World War I cryptanalyst who manages a dedicated team of female codebreakers known as Dilly's Fillies. He operates with a philosophy of lateral thinking, frequently writes poetry, and acts as a father figure to his staff.

A handsome royal serving in the British Navy. Eager to prove his loyalty to Britain and distance himself from his German relatives, he actively pursues combat roles while courting Osla.

Beth's parents, Muriel and her passive husband. Mrs. Finch is highly controlling and emotionally abusive, relying on her daughter for household chores and aggressively enforcing strict religious and behavioral rules.

Mab's four-year-old daughter. To protect her from the social stigma of illegitimacy, she is raised to believe Mab is her older sister. She is the driving force behind Mab's fierce ambition.

A skilled cryptanalyst and member of Dilly's Fillies. She helps introduce Beth to the grueling, complex daily work of breaking Enigma ciphers.

Harry's wife. She married him after an unplanned pregnancy but maintains a friendly, open marriage with him for the sake of their son, pursuing her own romantic interests on the side.

Harry and Sheila's young son. He suffers from polio and occasionally faces bullying, prompting fierce protectiveness from his father.

A mysterious man who aids Osla while she is in shock, wrapping her in his coat with the initials J.P.E.C. before disappearing into the chaos.

An authoritative figure at Bletchley Park who commits the new recruits to absolute secrecy under the Official Secrets Act.

Osla's friend from the factory who sets her up on the blind date with Prince Philip.

Dilly Knox's welcoming and supportive wife, who opens their home to the young cryptanalysts.

A scruffy stray schnauzer dog that Beth brings home, representing her first major act of defiance against her controlling mother.