The action takes place in England, at the end of 1586 – beginning of 1587. In the castle of Fotringe, her half-sister, Maria Stewart, was imprisoned on the orders of the Queen Elizabeth of England, claiming the throne of England. With her, her nurse Anna Kennedy. Despite the severity of detention and many deprivations, Maria continues to remain adamant. She repeatedly managed to bribe the guards and organize conspiracies against Elizabeth.
Her last guard, Flight, is extremely strict towards her. But recently in Fotringei appeared his nephew Mortimer, who returned from wandering around France and Italy, where he accepted Catholicism. In the same place, he became a supporter of Mary and now he came to England to free her. On his side are twelve reliable warriors who agree to help. Mortimer reports that the trial of Mary was held in London and she was sentenced to death. The Queen warns the young man that in the event of a failure of his escape, death awaits him. Mortimer is adamant in his desire to free Lady Stewart. Following him, Maria wrote a letter to Count Leicester in London, she hopes that he will help Mortimer and her.
In the Palace of Westminster at the court of the Queen discuss the upcoming marriage of Elizabeth with the Duke of Anjou. The Queen himself reluctantly agreed to this marriage. She is forced to think about the desire of her subjects to have a legitimate heir to the throne. But now Elizabeth’s thoughts are occupied by another – she will have to confirm the court’s decision on her half-sister, Maria. Most noblemen from the encirclement of the English queen, led by Lord Burley, support the verdict of the court. Lady Stuart is approached only by the old Earl of Shrewsbury, timidly supported by him and Count Leyster.
In the palace appear Flight with his nephew. The flight sends Elizabeth the letter of the prisoner with a request for a personal meeting. In the eyes of the queen, when reading the letter, tears appear, those around are already ready to understand them as a sign of mercy to their sister. In fact, the English queen asks Mortimer to secretly kill her rival, but so that no one realizes that the blow was inflicted by the royal hand. The nephew of Flight agrees, because he understands that only by deceit he can take away trouble from Lady Stewart.
Left alone with Count Leicester, Mortimer gives him a letter to Maria. It turns out that the earl has been the favorite of Queen Elizabeth for ten years, now her marriage to the young, handsome French duke finally deprives him of hope not only on her hand, but also on her heart. The letter of Lady Stewart again inspires him with a hope for the royal throne. If he helps her get free, then she promises him her hand. But Lester is cunning and very careful, he asks Mortimer never to mention his name in conversations, even with his like-minded people.
The Count proposes to arrange a meeting between Elizabeth and Maria, then, he is sure, the execution will be canceled, and later it will be possible to talk about the future. A young man does not like this kind of circumspection, he asks Leicester to lure the Queen of England into one of the castles and keep her locked up there until she orders to release Maria. Count on this is not capable.
Leicester realizes his plan. On a date with Elizabeth, he manages to persuade her during the hunt to turn to the castle-prison of Mary and meet with that unexpectedly, during her walk in the park. The Queen agrees to the “extravagant” offer of her lover.
Unsuspecting Maria rejoices at the permission to take a walk in the park, but Flight informs her that her meeting with Elizabeth is waiting for her here. In the first minutes of the meeting, a beautiful prisoner rushes to the feet of her crowned sister with the request to cancel the execution and release her, but Elizabeth tries to humiliate Lady Stewart, reminding her of her failed personal life. Unable to overcome her insane pride and lose control of herself, Maria reminds her sister that she is... an illegitimate child, not a legitimate heiress. Enraged, Elizabeth hastily withdraws.
Maria realizes that she destroyed her hope for salvation with her own hands, but Mortimer comes in informing me that this night he and his men will seize Fotringei with force and release her. For his boldness, the young man expects to receive a reward – the love of Mary, but she refuses to him.
The park around the castle is filled with armed people. A friend of Mortimer brings the news that one of their supporters, the Toulon monk, committed an attempt on Elizabeth’s life, but his dagger pierced only the mantle. The conspiracy is revealed, the soldiers of the English queen are already here and must urgently run, but Mortimer is blinded by his passion for Mary, he remains, to either release her, or die with her.
After an unsuccessful attempt on Elizabeth’s life, since the murderer turned out to be a French citizen, the French ambassador is urgently expelled from England, and at the same time the marriage agreement is broken. Burley accuses Lester of malicious intent, because he enticed Elizabeth to meet with Lady Stewart. Mortimer comes to the court, he informs Leicester that during the search of Mary, drafts of her letter to the count were found. The sly lord orders to arrest Mortimer, realizing that if he informs him of the disclosure of his conspiracy against Elizabeth, he will be counted on it when he answers for Maria’s letter to him. But the young man is not given into the hands of the officers and, in the end, sticks himself.
At an audience with Elizabeth Berly, she shows Maria Stuart’s letter to Count Leicester. The humiliated queen is already ready to approve the death sentence of the depraved woman, but Leicester breaks into her chambers. He reports that the monk seized after the assassination is only a link in the chain of conspiracy, the purpose of which was the release of Lady Stuart and her elevation. Indeed, he corresponded with the prisoner, but it was from his side only a game to be aware of what is happening and in time to protect his monarchy. He had just been seized by the initiator of the conspiracy – Sir Mortimer, but he managed to kill himself. Generous Elizabeth is ready to believe her lover, if he himself will carry out the death sentence of Mary.
Indignant people under the windows of the royal palace demanded the death penalty for Lady Stewart. After reflection, Elizabeth still signs the court’s decision on the execution and hands it to her secretary. In the paper it is said that the Scottish queen must be executed at dawn. The secretary hesitates whether to give this document for immediate execution, but the lord Burley, who was in the waiting room, pulls the paper out of his hands.
In the courtyard of the castle Fotringay they build a scaffold, and in the castle Maria bids farewell to her close people. Lady Stewart is calm, only in private with her butler Melville, she admits that her secret desire was to communicate with a Catholic confessor. The old man reveals to her that he has accepted the order and now is ready to let her all her sins. The last request of Mary is that after her death everything was exactly fulfilled according to her will. She asks her to send her to France and bury her there. Appears Count Leyster, he came to fulfill the order of Elizabeth – to accompany Mary to the place of execution.
At this time in the royal castle, Elizabeth is waiting for news from Fotringei. To her comes the old Earl of Shrewsbury, who reports that the scribes of Mary, who in court showed her guilt as guilty of an attempt on the English throne, declined their words and confessed their slander to Lady Stewart. Elizabeth pretended to be repenting in her signature by the court decision and blames the blame on her slow-moving secretary. Lord Burley enters. Maria Stuart is executed. Elizabeth accuses him of hasty execution of the sentence. Lord Shrewsbury announces his decision to retire from the court. The Count Leicester departs immediately after the execution of Mary in France.