Magnus is a high-ranking British intelligence officer stationed in Vienna. Following his father's funeral, he goes missing rather than returning to his wife and post. Hiding in a quiet boardinghouse, he begins writing extensive letters to his loved ones detailing his past. He possesses a lifelong habit of altering his identity and biography to please those around him and survive in the espionage world.

Rick is Magnus's father, operating primarily as a charming con man. He moves through extreme financial highs and lows, running fraudulent schemes that occasionally land him in prison. He expertly manipulates people for financial gain and teaches his son how to bend the truth to get out of difficult situations.

Axel is a German student with a mysterious past who shares a lodging house with Magnus in Bern. He acts as a tutor in the German language and socialist literature. Despite periods of separation, his connection with Magnus forms one of the most significant bonds in the spy's life.

Jack is a veteran British intelligence officer who recruited young Magnus in Bern. He holds a decorated military record from World War II and represents the old guard of British espionage. When Magnus vanishes, Jack launches a frantic investigation to locate his protégé and protect the agency's secrets from American scrutiny.

Mary is Magnus's wife, living with him in Vienna and acting as a dutiful hostess for his diplomatic cover. As the intelligence services search her home, she slowly realizes she knows very little about her husband's true activities. Frustrated by the patronizing attitude of his colleagues, she begins her own independent efforts to find him.

Miss Dubber operates a guest house in a small coastal town in Devon. She knows Magnus under the alias Mr. Canterbury and provides him with tea and a quiet space to write. She remains entirely unaware of his true identity or his career in international espionage.

Tom is the teenage son of Magnus and Mary Pym. He attends a British boarding school and serves as a prefect. He becomes a target for Jack Brotherhood's gentle interrogations as the agency attempts to trace Magnus's recent movements in Greece and Britain.

Lippsie is a Jewish German refugee who flees to Britain to escape the Nazi party. She becomes romantically involved with Rick Pym and acts as a devoted caretaker to young Magnus. She suffers from deep anxiety regarding the family she left behind in Germany.

Grant is an ambitious American intelligence officer stationed in Vienna. Relying heavily on computer data and behavioral analysis rather than traditional instinct, he attempts to convince his British counterparts that Magnus poses a significant security risk.

Peggy is a widow who lost her farm and her husband's insurance payout to one of Rick Pym's investment schemes. She actively searches for proof of his crimes and confronts him publicly, forcing young Magnus to acknowledge his father's destructive nature.

Dot is Magnus's mother and Rick's wife. She struggles to cope with the chaotic, criminal lifestyle imposed by her husband and eventually requires treatment in a psychiatric hospital.

Belinda is Magnus's first wife. They correspond during his early postings in Europe and marry just as he begins his formal spy training, though their union ultimately dissolves when he is sent to Berlin.

Sabina works as a Czech interpreter for the British in Graz. She assists Magnus in interviewing Eastern European refugees and develops a romantic relationship with him while teaching him her language.

Syd is an associate of Rick Pym who assists with his political campaigns and financial frauds. He remains loyal to the Pym family, refusing to cooperate fully with Jack Brotherhood's investigation.

Major Membury serves as Magnus's intelligence tutor in Graz. He instructs the young officer in tradecraft and the recruitment of foreign sources, later speaking with Jack Brotherhood during the search for Magnus.

Kate is a colleague of Jack Brotherhood who once had a romantic affair with Magnus. She secretly helped Magnus alter his personnel files to protect his career progression.

Sefton is Magnus's friend from boarding school and Oxford University. He receives a drunken, apologetic phone call from Magnus shortly after Rick Pym's funeral.

The Baroness is an associate of Rick Pym who claims to possess hidden family treasures in Switzerland. She recruits young Magnus for a retrieval mission, only to steal his funds.

Bee is Grant Lederer's wife. She attends diplomatic functions in Vienna and assists her husband by observing the interactions of other operatives and their families.

Fergus is a Home Office operative. Jack Brotherhood assigns him to monitor Mary Pym's house in Vienna under the guise of a grieving relative following Rick Pym's death.

Georgie is a British operative working alongside Fergus to supervise Mary Pym and search her home for evidence of Magnus's recent activities.

A Welsh priest who runs an Appeal Committee for his church. He challenges Rick Pym about missing charity funds, prompting Rick to devise a fraudulent explanation to cover the theft.

A generous Swiss man who operates a lodging house in Bern. He provides Magnus with a very small room and a stable domestic environment during the young man's time abroad.

Sefton Boyd's sister. She visits Oxford, where Magnus attempts to impress her with lies about secret missions in Switzerland before deciding she is too focused on romance.

Paul is Belinda's current husband. He is a left-wing activist and writer who builds a life with Belinda after her marriage to Magnus ends.