Sisi, the daughter of the Bavarian Duke Max, grows up carefree and close to nature with her siblings at Lake Starnberg. When the young Austrian Emperor Franz Joseph is to marry her older sister Helene, Sisi reluctantly goes along to Bad Ischl for the engagement. But a fateful encounter between Sisi and Franz suddenly changes the course of events.

Sisi has fallen in love with Franz. Without hesitation, she follows him to Vienna as his future wife. But the strict court ceremonial quickly gets to the freedom-loving Bavarian princess. Out of love for Franz, she is nevertheless prepared to put up with all the hardships and duties. She knows that she must first earn the respect of the court. Sisi finds a friend and confidante in Fanny, whom she smuggles into the palace as a maid under a false name.

The young couple's wedding night does not go as planned and Sisi needs Fanny's advice more than ever. But Countess Esterhazy exposes Fanny as an impostor and banishes her from court. It is only during their honeymoon in Laxenburg that Sisi and Franz slowly find their way to each other. At her first, official reception as empress, Sisi surprises everyone with her excellent knowledge of the Hungarian language and the kindness with which she treats the Hungarian nobility.

Sisi is pregnant. The young imperial couple do not have much time to enjoy their happiness together. The conflicts in Hungary come to a head, and the rest of Europe is also seething. Countess Esterhazy hopes that Sisi can persuade the Emperor to negotiate with the Hungarian nobility. She arranges a secret meeting between Sisi and Count Andrassy. But before she can speak to Franz, an assassination attempt is made on him during the christening of their daughter Sophie.

Franz barely survived the assassination attempt in the church. But when there are uprisings against the Habsburgs in Italy, he goes to war. To help the soldiers as well, Sisi helps out in a military hospital in Laxenburg and cares for the wounded. The mood in Hungary is still heated. Sisi succeeds in persuading Franz to meet Count Andrassy during a reception in Budapest and negotiate a peace treaty. At the height of the festivities, another dangerous incident occurs.

The new assassination attempt on Franz was prevented, but the young imperial couple is struck by a terrible blow of fate in Budapest. The little princess Sophie dies. Sisi falls into deep, immeasurable grief and Franz distances himself from her more and more. Fanny must pay for her crimes. In Europe the signs continue to point to war, Napoleon III claims parts of the Habsburg lands in Italy for himself. Sisi refuses to give up and fights - for herself, her people and her love for Franz!

Franz and Sisi are happy that there is an heir to the throne, but Sisi feels trapped in a golden cage. A new threat of war forces Sisi and Franz to travel to France.

At Count Andrássy's country estate, Sisi is reminded of the freedom of her childhood; as the courtly constraints slowly fall away from her, Sisi realises that the Hungarian people need her help more urgently; Sisi pledges her support to Andrássy.

The Hungarian rebel Ödön Körtek intends to kidnap Sisi; in joint captivity with Count Andrássy, Sisi is faced with the question of how long she can remain steadfast; Franz is confronted not only with his father-in-law, but also with Sisi's sister.

Sisi and Andrássy travel to Vienna to convince Franz of the need for a Hungarian parliament; Sisi tries to clear her head; the special affection between Sisi and Andrássy does not go unnoticed by Franz, who falls back into his old patterns.

While the war with Prussia poses problems for Franz, Sisi must now cope on her own in Vienna; in Hungary, Andrássy makes an attempt to defeat the cruel Körtek.

Sisi desperately tries to get closer to Franz again, but he refuses to speak to her and sends her back to Hungary; Sisi is to help Count Andrássy negotiate a new constitution with the Hungarians, and she does not yet suspect that it could be goodbye.

As Napoleon gets deposed, things start to become restless in Vienna; Franz thinks it wise to let Rudolf start his military training earlier, against Sisi's wishes.

Sisi picks up Rudolf and leaves Vienna, giving Franz an ultimatum that she will only return if she can decide how her son will be raised; Franz tries to reduce the unrest among the workers.

Sisi and Rudolf enjoy their freedom on the island; through a spy, Franz, fearing new alliances in Vienna, discovers the whereabouts of his wife and son.

Franz joins Sisi and Rudolf in France, but political and personal challenges strain their relationship. After a night of passion, Franz secretly travels back to Vienna with Rudolf.

When Sisi learns that Franz has removed Rudolf from the army, she returns to Vienna. There, she has to negotiate the alliance and try to restore the tense atmosphere.

Sisi finds out that a worker has kidnapped her son. In exchange for him, the kidnapper wants the emperor's life. Sisi wants to save Rudolf, but it is a perilous mission because the kidnapper has nothing to lose.