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.

When England's armies threaten Scotland's borders, Mary asks King Henry for help, but he refuses. Tomas, the son of the King of Portugal, proposes marriage to Mary, promising her aid against England if she'll abandon Francis and turn to Tomas instead. Francis puts Bash in jeopardy when he lets his feelings for Mary cloud his judgment.

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.

An ex-lover of Francis' arrives and brings danger with her, so Bash consoles an uneasy Mary. Meanwhile, Queen Catherine persuades Aylee to snoop on Mary; and Bash lands in hot water with heretics, who accuse him of disrupting a sacred ritual.

An attempt to scare Mary causes Queen Catherine to take drastic measures to make sure the guilty party is caught. Francis, aware of Bash and Mary's growing attraction, turns to Olivia. Bash ventures into the woods to pay his debt - the human sacrifice the pagans demand - and returns with blood on his hands. Meanwhile, Kenna comes clean with the girls about her affair with the King, to a mixed response.

The King goes to war as an unlikely intruder locks down the castle. Mary and Francis realise they must overcome their argument and work together to save everyone at court.

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,

When a plot to kill Bash goes wrong, Queen Catherine is suspected of orchestrating it. Mary offers to help free a wrongly imprisoned pregnant peasant named Isobel who has a mysterious tie to Bash. Meanwhile, Lola blackmails Queen Catherine to keep her from trying to ruin Mary and Bash, whose bond continues to grow.

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.

It appears to be time for Mary to choose. She has to marry either Francis or Bash taking into account her country's needs as well as her own. This decision gets harder when Francis comes to court with Lola by his side after he saved her in the last episode. It gets even more complicated when Mary's mum comes to France with her own ideas about Mary's future.

Two months after becoming married, Mary and Francis must rejoin court after their idyllic honeymoon. Upon returning, secrets they hoped to bury start coming out. Meanwhile, King Henry and Queen Catherine bond over spilled blood.

As women in the castle mingle with possible suitors, Lola is reluctant to participate. Kenna fears for her safety after another violent incident with King Henry. Bash determines to uncover the truth about the darkness.

When Francis reluctantly agrees to help Bash uncover the threat in the woods, he ends in grave danger, with only Bash to save him. Meanwhile, the King's madness causes chaos when a servant wins "Queen for the Day," and the King becomes obsessed with her. The King also forces a surprising, and unbreakable, union with a new couple at Court. Meanwhile, Greer gets caught kissing kitchen servant Leith, which threatens to ruin her.

Mary uncovers her marriage contract's secret clause.

When Mary's brother James arrives in France and convinces Mary to return to Scotland, Francis is suspicious and uncovers a plot that would destroy Mary, which causes a rift between them. King Henry's downward spiral continues, leaving Penelope in charge, causing Catherine and Kenna to take drastic measures. Meanwhile, Lola becomes wary of Lord Julien's motives behind his marriage proposal.

Mary and Francis are forced to make difficult choices between Scotland, France, or their marriage; Mary's uncle brings bad news regarding Marie de Guise; Henry makes some bad choices for France; Bash and Kenna continue to work on their marriage.

Mary enlists a mercenary to help her, which forces her to realize there are sacrifices and lives she is willing to risk to save her country. Francis embraces his role as Dauphin to lead France in a brutal battle against England, and finds a new ally in Leith. Meanwhile, as Lola grows closer to Lord Julien, she gets increasingly suspicious that he is going to betray her.

Mary and Catherine form an unlikely alliance when deciding how to deal with the increasingly manic King Henry, which puts Francis in jeopardy. Bash finds a boy who lived to tell about his encounter with the Darkness, which makes Bash determined to end it for good at any cost. Lord Julien (guest star Giacomo Gianniotti) reveals the truth about his motives, and Lola, blinded by love, finds herself in a dire situation after she attempts to protect him.

Henry plots to kill Francis, and begins his efforts to woo and marry Mary. Leith returns to win Greer back. Lola goes into labour. Francis, Catherine and Mary plan a coup. The Darkness returns for Pascal.