A resilient young French woman managing her family's hotel in the German-occupied town of St. Péronne during World War I. While her husband fights at the front, she assumes the role of protector for her siblings and community, using her wits to secure basic necessities. Her most prized possession is an oil portrait of herself, a constant reminder of the vibrant life and love she experienced before the war.

A 32-year-old widow living in contemporary London in a striking, minimalist home called the Glass House, designed by her late husband. Emotionally isolated and struggling with mounting financial debt, she clings to a painting titled "The Girl You Left Behind," a honeymoon gift that anchors her to her past. She resists moving forward with her life, using rigorous daily routines to block out her profound grief.

The newly appointed German commander overseeing the occupied town of St. Péronne. An educated man with a deep background in art, he finds himself captivated by Sophie's portrait and the civilized world it represents. He enforces brutal military rules and requisition orders while simultaneously seeking intellectual conversation, creating a highly unpredictable dynamic with the starving townspeople.

An American former police officer now working in London as a director for the Trace and Return Partnership (TARP), an agency that recovers stolen art. Driven by a strong sense of professional ethics, he believes historical wrongs must be corrected regardless of the passage of time. His orderly, justice-oriented life becomes complicated when his personal feelings clash with a major restitution case.

Sophie's older sister and co-manager of Le Coq Rouge. With her husband away at war, she bears the heavy responsibility of caring for her two young children in a starving, occupied town. More cautious than her sister, she frequently worries about the dangers of drawing the occupying army's attention and prefers to maintain a low profile.

A passionate, unconventional French artist and Sophie's husband, currently away fighting at the front lines of World War I. Before the war, he studied under master painters in Paris and introduced Sophie to a vibrant, bohemian lifestyle. His artistic vision of his wife, captured on canvas, serves as her emotional anchor and source of courage during the occupation.

A resident of St. Péronne who stands out due to her access to quality food, warm coats, and decent shoes during a time of extreme deprivation. The townspeople ostracize her, assuming she secures these privileges by offering favors to the occupying forces. She survives the hostile community while caring quietly for her young daughter.

Liv's former university classmate who works in the service industry and secretly sleeps at her workplace due to housing issues. Pragmatic, cynical, and highly resourceful, she moves into Liv's home and immediately begins challenging Liv's self-imposed isolation, offering blunt advice and practical assistance with overdue bills.

Liv's late husband, a successful and visionary architect who died suddenly four years prior to the story's modern events. He purchased the portrait "The Girl You Left Behind" during their honeymoon in Barcelona. His professional legacy, charitable foundation, and memory cast a massive shadow over Liv's present choices.

Sophie and Hélène's teenaged brother, who lives with them at the family hotel during the war. Still young and impulsive, he struggles to comprehend the nuanced, dangerous compromises his sisters must make to keep the family safe under strict military occupation.

Paul's colleague and business partner at the Trace and Return Partnership. She approaches the business of art restitution with a strictly pragmatic, commission-driven mindset, prioritizing the firm's financial viability over the emotional nuances of individual claims.

David Halston's former business partner who continues to run their architectural firm after David's death. He attempts to offer Liv practical, if sometimes unwelcome, advice about her financial difficulties and the realities of maintaining David's professional legacy amidst public controversy.

Liv's father, a man whose chaotic romantic life often requires Liv to step in as the responsible party. Despite his personal disorganization and occasional absent-mindedness regarding important dates, he offers his daughter genuine affection and a steady, non-judgmental presence.

Paul's brother, who provides a lively, familial contrast to Paul's intense professional life. He operates a local bar and frequently acts as a sounding board for Paul's personal and professional dilemmas, offering practical support and a place to stay when crises arise.

Liliane's young daughter, growing up in the hostile, starving environment of German-occupied St. Péronne. She relies entirely on her mother for protection against both the deprivations of war and the harsh judgments of their neighbors.