The Other Boleyn Girl is a historical drama based on the relationship between Anne Boleyn's sister, Mary and King Henry VIII. During 16th century England, Henry VIII is married to Catherine of Aragon, who is unable to produce a male heir. Henry soon tires of his marriage to Catherine and his eyes begin to wander. Catherine's inability to bear a son is seen as an opportunity for Anne's father Thomas Boleyn and his brother-in-law Thomas Howard. The duo conspire behind the scenes to have Anne installed at King Henry's court. When Anne arrives, the king quickly becomes smitten and visits the Boleyn estate. During the visit, Henry is injured while on a hunting expedition. His attentions quickly turn to Anne's sister Mary, who nurses Henry back to health.
Henry invites Mary to court. She is reluctant to go because she has a husband and knows that Henry is trying to manipulate the situation to his advantage. When Henry sends Mary's husband away, she finds herself falling for Henry's charms. Anne is non too pleased by the situation and rebels. After Anne enters an ill advised marriage to Henry Percy, Mary gets wind of the situation and tells her father and uncle. The marriage is annulled, which makes Anne and Mary enemies.
Mary finds that she is carrying Henry's child. The impending birth gains the Boleyn family great favor for the time being. Anne schemes to pull Henry away from Mary, which is successful. Soon after, Mary gives birth to Henry's son. She has Mary banished to the country, and convinces Henry to have his marriage to Catherine annulled. Although Anne is victorious in her scheming, her happiness doesn't last long. She soon finds herself in the same position as Catherine--unable to have a son.
Henry has now grown tired of Anne, and his wandering eye catches sight of Jane Seymour. Now that Anne has miscarried his son, he wants to rid himself of her for good. Anne and her brother George are arrested and convicted on false charges of treason and incest. Mary arrives from the country to ask Henry to spare her sister's life. Although Henry seems as though he is receptive to granting Anne a reprieve, he changes his mind at the last minute and has her executed. Mary married William Stafford and never returned to court again.