Season 4
The fourth and final season covers Henry's ill-fated marriage to Catherine Howard and his final, more congenial marriage to Catherine Parr. The ageing King seeks military glory by capturing Boulogne, France. In his final hours, he is troubled by the ghosts of his dead wives.
Henry marries 17-year-old Catherine Howard and is besotted by her beauty, calling her "his rose without a thorn", and feels rejuvenated. Catherine starts to dally with the King's groom, Thomas Culpepper, and is encouraged by her senior lady-in-waiting, Lady Rochford — Henry's sister-in-law via Anne Boleyn's brother — who is also being bedded by Culpepper. In episode 2, Henry invites his former wife, Anne of Cleves, to court to celebrate Christmas as he wants to reward her for keeping her word to him and for her loyalty. She, in turn, is grateful for the charity he has shown towards her. After the festivities, he is struck down once again by his leg wound — from his former jousting days — while Catherine is with Culpepper.
Feeling the need for company, Henry visits Anne of Cleves and has a brief liaison with her. He and Catherine embark on the royal Passage to the North to forgive the former rebels, accompanied by Princess Mary, who is popular with the King's northern subjects. It is during this period that Catherine and Culpepper consummate their relationship and Catherine falls in love with him. In episode 4, Henry makes friendly overtures to the French ambassador, hoping to prevent an invasion, and Francis Dereham, Catherine's former lover when they both resided with the Dowager Duchess of Norfolk, arrives at court and blackmails the queen into making him her private secretary. Some weeks later Henry receives a secret letter about their prior sexual exploits.
In episode 5, the King grants permission to the Earl of Hertford to investigate the queen's alleged liaison with Dereham. He plans to pardon her but is then informed by his Council of her affair with Culpepper — revealed by Dereham under torture — and he has all three executed, along with Lady Rochford, who has gone mad in the Tower. On the scaffold, Catherine states that, although Queen of England, she would have preferred to have been Thomas Culpepper's wife. In episode 6, Henry is courted by both Spain and Rome to form a military alliance against the French, who have allied with the Turks, and he is persuaded to form an alliance with the Holy Roman Emperor and invade France. Thomas Seymour introduces Catherine Parr at court, and she catches the king's eye, even though she is married. Henry pursues her and sends Seymour to the Low Countries to remove him as a love rival.
Military preparations are made, and English troops lay siege to Boulogne, bombarding it with cannon as an Italian engineer digs a tunnel to blow up the castle. Charles Brandon captures a French father and daughter and falls in love with the daughter, Brigitte. At home, Catherine Parr is acting as regent in Henry's absence and uses her power to further the Protestant cause but is checked by Bishop Gardiner and his Catholic faction, supported by Princess Mary. In episode 8, the castle of Boulogne is overcome and the keys to the city handed over to Henry by the French mayor. Henry returns to court in triumph, leaving the Earl of Surrey in charge of the new possession.
At home, Henry is disturbed by the struggle between the Catholic and Protestant factions, and Catherine alienates him through her support of the Protestant reformation. Bishop Gardiner continues his campaign against Protestants and gathers enough evidence to persuade the king to issue an arrest warrant against the queen for heresy. In the meantime, Henry Howard, now Lieutenant General Surrey, loses a disastrous battle at Boulogne, and whilst making an attempt to usurp power from the 'new men' like the Seymours and Richard Rich, he is arrested, tried for treason, and executed, despite the paucity of evidence against him.
In episode 10 an increasingly frail Henry is facing his own mortality. His mind is on the succession, and he appoints the Earl of Hertford to be Lord Protector until Prince Edward comes of age. Catherine, knowing the mortal danger she is in, orders her ladies-in-waiting to destroy all their heretical books and no longer to discuss religious matters; she also submits herself to her husband, and he pardons her. The dying Charles Brandon is reunited with Henry for one final and nostalgic meeting. As the king's own end approaches, the ghosts of Henry's first three wives confront him over their deaths and his treatment of their children. Henry orders his family to spend Christmas at Greenwich, bidding them his final farewell and instructing the princesses Mary and Elizabeth to care for their brother. The final scene has him approving the portrait painted for him by Hans Holbein, depicting him as a virile, youthful King.