Austria, late 19th century. Countess Irma Sztáray (Sandra Hüller) leaves her home in Hungary to become the lady-in-waiting for Empress Elisabeth of Austria (Susanne Wolff), known to those close to her as Sisi. Irma falls under the spell of the rebellious Empress Sisi, and the two form a strong bond during a summer retreat in Greece. However, once home in Vienna, their lives take dramatic and irrevocable turns.