Set in mid-16th-century England during intense religious and political upheaval, the novel follows three Grey sisters, each narrating her own section, as they navigate their dangerous proximity to the English throne. The Greys descend from Princess Mary, favorite sister of King Henry VIII, making them heirs to the crown after King Edward VI and his half sisters, the Catholic Princess Mary Tudor and Princess Elizabeth, whose religious leanings remain uncertain.
The first section belongs to Jane Grey, the eldest, a 12-year-old zealous Protestant scholar living at Bradgate House in 1550. Jane considers herself the greatest young scholar in Europe, mentored by the late Queen Kateryn Parr. She introduces her sisters: Katherine, nine, whom she finds frivolous, and Mary, five, born very small with a twisted spine. When Edward Seymour, Duke of Somerset, visits with his son Ned to arrange a betrothal, Jane remains outwardly stiff, though privately pleased by Ned's charm and devotion to the reformed faith.
Political fortunes shift rapidly. Somerset is executed for conspiring against John Dudley, the new lord president of the Privy Council, the king's governing body, ending the betrothal. King Edward's health deteriorates, and Jane's father explains that the dying king intends to bypass both half sisters and name a Protestant successor. Jane, Katherine, and little Mary must all marry at once so that one might produce a male Tudor heir. Jane is matched with Guildford Dudley, John Dudley's son. She protests that she is already formally promised in marriage to Ned, but her mother forces her to comply. The lavish joint wedding takes place at Durham House in May 1553.
When King Edward dies, Jane is taken to Syon House, where John Dudley and the assembled lords announce she has been named queen. Jane is horrified, but her parents, in-laws, and councillors insist. At the Tower of London, Guildford demands to be crowned king; Jane refuses, declaring she alone was named heir. Her reign collapses within days as Princess Mary raises her standard and gathers supporters, the Privy Council defects, and Jane's father tears down the cloth of estate, the ceremonial canopy marking royal authority, over her chair. Jane replies she removes her royal robes more willingly than she put them on and is imprisoned as Mary I takes the throne.
Jane spends months in the Tower, confident Queen Mary will show mercy. She is tried for treason at London's Guildhall and sentenced to death but believes the sentence is merely a threat. Then her father raises a rebellion whose failure seals her fate. John Feckenham, a Benedictine monk, visits Jane to confirm her execution and reveals that her father rose not for her but for Princess Elizabeth. Jane refuses to recant her Protestant faith. On February 12, 1554, she watches Guildford's headless body pass her window in a cart, then walks to the scaffold. After affirming her faith in a speech, she is blindfolded and panics, crying, "What shall I do? Where is it?" before someone guides her hands to the block.
The second section is narrated by Katherine, who reads Jane's final letter with fury. It is a cold sermon rather than a personal farewell, though Katherine recognizes Jane intended it for publication as a martyrdom text. Katherine's own marriage to Henry Herbert has been annulled, and their father is executed for his role in the rebellion. Their mother, Lady Frances, secures a partial restoration of the family's fortunes, and Katherine returns to court as a lady-in-waiting to the queen who executed Jane.
When Queen Mary dies and Elizabeth takes the throne, Katherine is marginalized at the new court. She befriends Janey Seymour, Ned's sister, and falls in love with Ned through visits to the Seymour home at Hanworth. Katherine's mother blesses the match but dies before writing the formal letter requesting Elizabeth's permission. In December 1560, Katherine and Janey walk to Ned's house in Cannon Row, where a hastily found minister performs a brief ceremony. Ned gives Katherine a wedding ring with five hidden golden links. Months later, Janey dies, leaving Katherine without her only witness and go-between. William Cecil, Elizabeth's chief advisor, arranges for Ned to travel to France. Katherine, now uncertain about a possible pregnancy, lets him go. Her letters go unanswered; they are being intercepted.
Katherine's pregnancy becomes undeniable. She confesses to Robert Dudley, Elizabeth's favorite, who tells the queen. Elizabeth says nothing during the summer progress, the queen's traveling tour of the countryside, but has Katherine arrested and sent to the Tower upon their return to London. Ned is recalled from France and imprisoned above her. Their accounts match under interrogation, but the missing minister, dead witness, and stolen papers leave no proof of the marriage. Katherine gives birth to a son, Edward, called Teddy. Archbishop Matthew Parker declares the marriage invalid and the child illegitimate.
The Tower's governor-jailer allows Ned to visit Katherine at night, and she becomes pregnant again, giving birth to a second son, Thomas. Elizabeth permanently separates the couple, sending Katherine to her uncle's house and Ned to his mother's estate while keeping their elder son Teddy from Katherine. Over the following years, Katherine is moved from guardian to guardian as Elizabeth refuses to name her heir despite pressure from parliament and the council. Katherine sinks into despair, refusing to eat. In January 1568, she dies aged 27, sending Ned her rings and a mourning ring engraved "While I lived, yours."
The final section belongs to Mary Grey, the smallest sister, who narrates as a confident, pragmatic woman under four feet tall. She has quietly fallen in love with Thomas Keyes, the queen's sergeant porter, the official who oversees the palace gate, a man nearly seven feet tall. In the summer of 1565, during a court wedding, Mary and Thomas marry secretly in his rooms above the palace watergate. Elizabeth discovers the marriage almost immediately. Mary is confined at Chequers in Buckinghamshire in a single tiny room. Thomas is imprisoned in the Fleet Prison in a cell so small he cannot stand upright, hunting sparrows from his window to survive. Mary writes desperate letters renouncing her marriage and begging for Thomas's release.
She endures years of captivity, watching as Elizabeth manipulates the succession, as Mary Queen of Scots is defeated at the Battle of Langside, flees to England, and is imprisoned, and as Katherine wastes away. Mary writes to Katherine urging her to eat and live, insisting that Jane's advice to learn to die was wrong. When Katherine dies, Mary receives Mr. Nozzle, Katherine's elderly pet monkey, now wearing mourning ribbons. Thomas is eventually released to Sandgate Castle in Kent and writes Mary a tender letter promising to wait. Before they can reunite, he dies. Mary collapses and spends months in bed but eventually rises, reasoning she will not give Elizabeth the satisfaction of another dead cousin.
Elizabeth finally releases Mary without explanation and restores her allowance. Mary buys a house in London and lives as an independent widow, keeping Mr. Nozzle on a red velvet cushion dressed in Tudor green. She wears perpetual mourning black with a scarlet petticoat underneath: red for defiance, for life, and for love. She reflects that her small life has been a life of greatness, and that if Elizabeth outlives her, the queen will at least give her a magnificent funeral, "fit for the last Tudor princess."