Isabelle Laustin, a 15-year-old Parisian aristocrat, is the daughter of Leon and Marie Laustin and younger sister to Geneviève. Initially a tomboy drawn to rough play, she matures into a proper young lady captivated by Captain Victor, envisioning dances and engagement. Her sheltered world shatters when Napoleon III's defeat at Sedan forces her family to flee besieged Paris. Disguised as a boy, Isabelle escapes to Versailles and then London. This disguise proves essential for her work gathering intelligence against Prussian forces and collaborators like the corrupt official Thiers. Her relationships are complex: she repeatedly rejects marriage proposals from her friend Jean, once throwing his bouquet back, declaring him "ten years too young." She also navigates family strife stemming from Geneviève's forbidden relationship with Jules, a commoner pianist and revolutionary leader, which results in Geneviève's disownment. Through the conflict, Isabelle transforms from a protected girl into an active resister, conducting espionage, aiding tactical operations like repairing General Gambetta's escape balloon, and witnessing rising violence. Tragedy strikes during the Bloody Week massacre (1871), claiming Victor, Jean, Jules, Geneviève (and her unborn child), and other allies. As the sole survivor of her family and circle, Isabelle confronts the ruins of Paris. The episode title "Departure for a New Life" implies her relocation, likely to London, to rebuild.