Seventeen-year-old Effi Briest (Julia Jentsch) is pressured into marrying Baron Geert von Innstetten (Sebastian Koch), a man more than twice her age who once courted her mother. Moving to the dreary Baltic port town of Kessin, Effi finds herself isolated in a cold, strict household while her husband prioritizes his political career. Bored and starved for affection, Effi is drawn to Major von Crampas (Mišel Matičević), a charming military officer. They enter into a passionate, secret extramarital affair. Years later, after the couple has relocated to Berlin, Innstetten discovers the old love letters between Effi and Crampas. Bound by rigid Prussian codes of honor, he challenges Crampas to a duel and casts Effi out of her home, forbidding her from seeing her daughter.