Somerset has lost the power struggle with Northumberland and is executed. Northumberland, ruler of the realm due to Edward VI's minority, sees that the succession is key as Edward is unmarried. He will call on his friend Suffolk, Henry Grey, as Suffolk's wife, Frances Brandon, granddaughter of Henry VII, and their daughter Jane Grey, follow Henry VIII's daughters in the line of succession.
Jane's great scholarship is made evident in a scene in which she interacts with and debates a priest who is a classical scholar. In the next scene, Edward notes "her learning is an example to us all."
Northumberland advises Frances that Edward is dying and their plotting to deny Mary and Elizabeth the throne begins. The plan is to get Edward to modify the line of succession to exclude his sisters and to have Frances defer the throne to Jane. To consolidate power, Suffolk agrees to have Jane Grey marry Guilford Dudley, Northumberland's son. Jane is cold on the idea, suggesting Edward would disapprove. Jane is beaten by her mother for this remark. Northumberland convinces Edward that the marriage is necessary for the Reformation. Jane is convinced by Edward to marry Guilford "for me."
Edward's health grows much worse. Northumberland asks the doctor to give Edward arsenic to keep him alive for a few extra days, which will buy Northumberland time to convince Edward to sign the document modifying the line of succession.
Guilford is found in a pub and advised he is to be married. In his first meeting with Jane, she makes it clear that her priorities are study and prayer and he notes that he is the type that likes pubs and prostitutes. Their wedding night is absurd, as Guilford falls asleep just moments after Jane enters the bedroom.
On a journey together, Guilford and Jane see commoners. Guilford offers one of them coins as alms. The commoner throws the money back, displaying that he wears the brand of a beggar, and yells "give us back our land," which could be a reference to the actions of Henry VIII, but more likely refers to enclosure. It makes little sense to Jane., but when they are next alone, Guilford explains what they had seen. He recounts a) confiscation of land during the dissolution of the monasteries, b) enclosure (fencing in) of common grazing land by landlords that ruined the livelihood of small landowners, c) and the inflation of the English currency. He notes that begging has been made illegal, and that those found begging were forced to wear a brand of disgrace. Jane, it seems, is learning that her quiet piety may not be enough to save the poor and transform England.
Northumberland attends to Edward, who is on his deathbed. He proposes the change to the line of succession, noting that Mary's succession would hurt England. Edward notes "but she's my sister." Northumberland cleverly replies "it's the duty of a Christian king to set aside the prejudices of the blood in favor of the greater good of God and country." Edward is sold on the necessity of modifying the line of succession and signs Northumberland's document.
Back at home, the newlyweds have another chat. "What do you wish for?", Guilford asks. When she replies with an idea that would improve England, he drops a glass full of wine, destroying it, and says "then it is done." She asks the same of him, gets a similar response, and similarly, but unexpectedly, destroys a wine glass. The game continues, to the delight of both. Jane has come out of her shell, daring to dream with Guilford of a better England. She is no longer a quiet, pious girl too busy with study and prayer to consider the plight of England, but a woman in touch with things a queen might dwell upon, though unaware of the plot to make her queen.
Northumberland now seeks the Privy Seal for the document proposing change to the line of succession. Some council members argue that, given Edward's infirmity, ratification might be treasonous, but they acquiesce when reminded that many English lands would revert to Rome if Mary became queen.
Northumberland's plot has nearly succeeded, but he is not able to apprehend Mary and Elizabeth. Edward dies and Northumberland fears to proclaim Jane queen with Mary and Elizabeth still at large. However, he decides that he must do so and calls a meeting, insisting that Jane and Guilford attend, but not telling them why their presence is required. Northumberland announces Edward's death and then proclaims that Jane is the new queen.
Jane's rejects the crown, shouting "no, it is not mine!" She learns that Guilford will be crowned king, and accuses him of having been in on the plot, but he convinces her this is not so. She accepts the crown. Her ascension is announced publicly, but meets more with confusion than joy. In a letter the privy council receives, Mary proclaims herself queen. Northumberland asks Suffolk to assemble an army to repel Mary. Queen Jane, unannounced, walks in on the meeting and changes the subject, demanding social reforms. Northumberland interrupts to request her signature on the document proposing the raising of an army by her father. Queen Jane refuses to sign unless Northumberland himself agrees to lead the troops that will defend her realm. He agrees and she signs. He proceeds to capture several supporters of Mary, but Jane has them all released. She hears that the campaign against Mary is failing. When Suffolk barges in on her and Guilford to advise them that Northumberland has been declared a traitor and that Mary has been named queen, ending Jane's nine day reign, things are clarified. Most unexpectedly, Jane's remark is "What a relief. Father, can we go home?" Predictably, though, Jane and Guilford are arrested, separated, and imprisoned in the Tower, as is Northumberland.
Mary rides triumphantly into England, and her first act is to free those incarcerated in the Tower for having opposed the Reformation, an ominous sign. Queen Mary speaks to Jane and makes it clear that, although a death sentence is near certain when Jane is tried, she intends to grant a reprieve. As Jane exits, the imperial ambassador enters, and Queen Mary advises him that she does not plan to execute Jane. The imperial ambassador notes that Phillip, with whom Queen Mary is in love, will not visit while Jane lives. Learning that her marriage appears to hinge on this execution grieves Queen Mary, who has suffered greatly from loneliness.
Suffolk advises his wife that he will join a revolt (which came to be known as Wyatt's rebellion) against Queen Mary. Jane learns that this revolt, with which she was unfamiliar, failed, and that Suffolk, who was one of its leaders, has been arrested. Jane and Guilford are tried, convicted and sentenced to beheading. Jane learns that Queen Mary, due to Suffolk's treason, will no longer grant a reprieve unless Jane embraces the doctrines of Catholicism, Predictably, Jane refuses.
Jane learns that Guilford has been executed on Tower Hill, and then she, herself, is led to the scaffold on Tower Green, where she is beheaded. Though still grievous of having had to execute Jane, Queen Mary is seen leaving the Tower, proclaiming "I am going to meet my husband."
A priest, the same one that had debated with Jane in the movie's opening minutes, looks to the heavens, reflects on Jane's life and quotes Plato in the movie's final line: "The soul takes flight to the world that is invisible but there arriving she is sure of bliss and forever dwells in paradise."