In England, Elizabeth is now being counseled by Catherine de Medici, together they seek Mary's downfall. In France, Francis must deal with his declining health.

As Francis' condition worsens he has plans for Mary's future and the next King of France.

When King Antoine makes an unexpected return. Mary and Francis turn to an unlikely ally to help hide Francis' condition and secure his family's future.

As the king Francis returns to life, Nostradamus is back with a new prophecy about his death. Meanwhile the English ambassador is offering Mary a chance at peace by signing away her claim to the English throne.

Claude is forced to marry someone selected by Narcisse. Meanwhile, a surprising discovery is made by Elizabeth, and it could alter her reign; and Mary asks Gideon to help her confirm her suspicions about Prince Don Carlos.

As she works to form political alliances, Mary tries to resist falling for Gideon; Catherine and Narcisse continue to battle for power over the Regency; Claude endures the fight of her life on her wedding night.

Charles' coronation gets closer as Mary discovers who poisoned Elizabeth and Catherine becomes a different kind of victim of the castle's killer.

Mary might have to sacrifice her cousin's life to save her own, as she and Gideon find themselves in uncharted emotional territory. Catherine's past returns to haunt her, while Lola and Elizabeth become unlikely allies.

When Mary returns to Scotland, she must keep her royal identity a secret as her country has taken a turn for the worse. Bash is kidnapped by druids. Elizabeth once again jeopardizes Lola's plans to leave England.

Mary and Bash race against time to stop anyone taking the Scottish throne. Catherine must help Charles.

Charles escapes the Red Knights, at the cost of an old friend. Mary returns home, but not everyone is happy. Narcisse's attempt to rescue Lola takes a twist when she chooses to carry out a risky mission.