Louise is a former Red Cross volunteer who now works part-time at a local thrift shop. During World War II, she found a profound sense of independence and purpose while distributing aid packages in Europe, creating a sharp contrast with her currently isolated, domestic life. When she discovers a familiar half-heart necklace in a donation crate, she is driven to investigate its origins and confront the unresolved mysteries of her past.

Helaine is a young Jewish woman living in Paris whose world is initially defined by a long, medically enforced confinement in her parents' elegant townhouse. Following a severe bout of childhood influenza, she escapes her isolation through books and stories until she finally ventures outside and falls in love. Her newfound freedom is soon threatened by the outbreak of World War II and the harrowing realities of the German occupation.

Ian is a dedicated volunteer manager for the Red Cross during World War II. He oversees the distribution of crucial care packages to POW camps across occupied Europe. Driven by his principles, he strictly adheres to the rules set by the occupying forces, insisting that the volunteers must prioritize their access to the camps above individual acts of rebellion.

Gabriel is a talented cellist who performs with the Orchestre National in Paris. He brings a sense of joy, art, and possibility into Helaine's highly restricted life, encouraging her to pursue her own independence. As antisemitism rises and the occupation begins, he is forced to make ethically fraught decisions to ensure his family's survival while maintaining his integrity.

Joe is a British combat veteran and Louise's husband. Having survived more than four years of active wartime service, he struggles deeply with unresolved trauma and painful memories. He copes by adopting a stoic facade and retreating into the quiet routine of a newly built suburban development, though his emotional distance creates a growing divide in his marriage.

Franny is a renowned actress and singer who uses her celebrity to perform for soldiers and POWs during the war. Beneath her glamorous exterior, she is a daring and compassionate woman who takes extreme personal risks to aid prisoners. Her sudden, highly suspicious death leaves a lasting impact on those who served alongside her.

Annette is Helaine's mother, a woman largely defined by her fear and protective instincts. Following Helaine's near-fatal childhood illness, Annette confines her daughter to their home for over a decade, attempting to create a perfectly safe, albeit restrictive, environment. Her own life is similarly constrained by a difficult marriage.

Otto is Helaine's father, a frequently traveling businessman who maintains strict control over his household. He demands obedience and is highly protective of the family's status, showing little tolerance for Helaine's desire to break free from her mother's imposed confinement.

Miriam is a Jewish prisoner held at Lévitan, having previously survived the brutal conditions of the Drancy transit camp. She is pragmatic, deeply knowledgeable about the store's covert operations, and fiercely brave, regularly risking her own safety to sabotage goods and assist the resistance.

Isa is a Parisian neighbor who invites Helaine to join her in cultivating food for their families as wartime rations grow scarce. She is a practical woman whose primary concern is the survival of her children, forcing her to make painful ethical choices as the German occupation tightens its grip on the city.

Midge is Louise's octogenarian boss at the local Oxfordshire thrift shop. She is an observant and supportive employer whose familial connections in the London jewelry business help Louise identify the mysterious origins of the half-heart necklace.

Beatrice, affectionately known as Bea, is Joe's sister and a widowed mother. She lives a conventional domestic life and frequently assists Louise with childcare, representing the societal expectations of postwar womanhood that Louise struggles to accept.

Maxim is a French guard who actively collaborates with the German forces at Lévitan. He is lecherous and predatory, using his modest amount of authority to intimidate, threaten, and proposition the vulnerable Jewish women imprisoned under his watch.

Henri is a former prisoner of the Lévitan department store who survived the occupation. Living quietly in postwar Paris, he serves as a crucial link to the past, providing Louise with essential information about the prisoners and the illicit flow of items during the war.

Ewen is the young son of Louise and Joe Burns. Raised in the quiet suburbs built over old bomb sites, he represents the innocent, postwar generation that his parents fought to protect, entirely unaware of the trauma his parents conceal.

Phaedra is Louise and Joe's young daughter. Like her brother, she is growing up in a peaceful era, wholly disconnected from the wartime anxieties that continue to divide her parents in secret.