After spending a childhood safely hidden away in a monastery, a teenage Mary Stuart arrives in France where she has been sent to secure Scotland's strategic alliance by formalizing her arranged engagement to the French King's dashing son, Prince Francis. Further complicating things is Bash, Francis' handsome, roguish half-brother and Francis' mother, Queen Catherine.

When Simon, an English envoy, tells Mary that the English are aware of her fragile engagement to Francis, Mary and Francis put on a show to protect their alliance.

Mary has to decide if she is willing to lie and sentence a man to death in order to have King Henry let her out of her engagement to Prince Francis. Meanwhile, Francis and Bash are suspicious of Tomas' true intentions which will ultimately lead to a confrontation with disastrous results.

Nostradamus tells Mary of his prophecy that one among them will die soon, which causes Mary to make a decision that will forever change her relationship with Francis.

When Mary and Bash are captured they are forced to return to the castle, tearing the bond of brothers apart and hardening Catherine's resolve to destroy Mary and Francis' love at any cost. Francis learns of the prophecy,

Henry returns from Rome unsuccessful, and accuses Catherine of adultery with Nostradamus with the goal of executing her. Catherine learns about Isobel's baby but the pagan mark on her foot is gone, making her useless as evidence against Bash. Mary and Bash learn that years ago Catherine had an affair and gave birth to a child before Francis was born. They inform Henry, who realizes that the father is his friend, Richard Delacroix, and has him imprisoned. Henry also rejects Catherine's attempts to out Bash and Diane as pagans, as he already knew about their heritage. Catherine has an encounter with Clarissa and, upon questioning Nostradamus, learns that the girl is a foundling who was disfigured by attempts Nostradamus' father made to remove a birthmark on her face; Clarissa is Catherine's daughter. Catherine attempts a murder-suicide with Mary, but Clarissa saves both of them, and Catherine is taken away to the tower to await her execution.

When Clarissa kidnaps the younger children of King Henry and Queen Catherine, Mary and Bash work with the Queen to find them, with tragic results. Meanwhile, when Lola attempts to help her brother with a debt he owes, Francis rescues her, causing the two of them to grow closer.

As Bash is being healed by the white witch, an old enemy shows up. Francis is on the edge of death and Mary must help Scotland from being under attack. Mary must make a decision to stay with Francis or go to Scotland with Conde.