Queen Elizabeth I has sent her beloved Robert Devereux, the Earl of Essex, to lead a military expedition to Ireland. Against the Queen’s orders, Robert has signed a peace treaty with the Irish rebels. Jealous of his favorable position with the Queen, her advisors seize the opportunity to push through a charge of treason against him.
Parliament prepares to discuss charges against Robert Devereux. Sarah, the Duchess of Nottingham and close friend of Queen Elizabeth, is plagued with guilt for being romantically involved with Robert prior to her marriage. Elizabeth arrives and expresses her love for Robert, and confides to Sarah that she suspects Robert of being unfaithful. The Queen is interrupted by a visit from Lord Cecil and Sir Walter Raleigh who convey Parliament’s frustration over her leniency towards Robert. To stall Parliament, she demands more proof of guilt before making a decision. When a page arrives with a request from Robert to meet with the Queen, her heart is stirred with a hope that their affection will be rekindled and she agrees to the visit.
Elizabeth meets Robert in private and tenderly reminds him of the ring she gave him, a special token that will guarantee his safety if he sends it back to her. Robert accidentally reveals that he is in love with another woman. Seeing Elizabeth’s initial anger escalate to fury, he tries to deny everything but the damage has been done: Elizabeth is set on vengeance against Robert and the unknown woman who has won his affection. With Elizabeth infuriated, Robert’s only remaining ally is the Duke of Nottingham (Sarah’s husband). Nottingham discloses to Robert that he observed his wife sobbing while embroidering a blue scarf and expresses his concern over his wife’s secret suffering. Their exchange is interrupted by Lord Cecil who summons Nottingham on behalf of the Queen to a meeting of Parliament to decide Robert’s sentence. Nottingham vows to save his friend.
Robert cannot resist seeing Sarah while Nottingham is out. He berates her for getting married while he was at battle. She explains that, after her father’s death, the union was ordered by the Queen to ensure her financial stability. Sarah also reminds him of his previous royal affection by pointing to his ring. They acknowledge their mutual love but realize that they can never be together. As a parting gift, Sarah gives her blue embroidered scarf. Robert accidentally leaves Elizabeth’s ring.
In the Great Hall at Westminster, Parliament reaches a decision and Lord Cecil informs the Queen of the verdict: the death penalty. Only Elizabeth’s signature is needed for the execution. She dismisses the court for a private meeting with Sir Walter Raleigh, one of her trusted spies. Walter informs the Queen that Robert was arrested with a blue scarf hidden under his shirt. Upon careful examination, Elizabeth notices love knots embroidered into the scarf, which confirm her suspicions, and fuels her agreement to sign Robert’s death warrant. Nottingham begs the Queen to have mercy on Robert. His pleas are silenced when Robert is brought in and Elizabeth reveals the blue scarf demanding to know its owner. Recognizing the scarf as belonging to his wife, Nottingham is horrified at Robert’s betrayal. In a fiery jealous rage, the Queen signs the death warrant.
Sarah receives a letter from Robert asking for Elizabeth’s ring as a means of preventing his execution. Nottingham returns and accuses Sarah of infidelity, ordering all doors locked to prevent Sarah from returning the ring.
Alone in the Tower of London, Robert reflects with regret upon his life of lies and indiscretions. He remains hopeful that Elizabeth will receive the ring and pardon him. The guards arrive and Robert allows himself to be led to his execution without protest. Elizabeth is deeply conflicted about having signed Robert’s death warrant. She desperately hopes Robert will return her ring to spare his life. To her horror, Cecil enters and informs her that Robert is being led to his execution. At that exact moment, Sarah bursts in and unable to speak, hands the ring to Elizabeth, confirming herself as the Queen’s rival. It is too late: a cannon shot is heard signifying the fatal blow has been delivered and Elizabeth lashes out at Nottingham and Sarah for their part in Robert’s death. Haunted by visions of Robert's severed head, Elizabeth longs for death. She declares James VI of Scotland the new King of England.