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.

After Mary receives an urgent message from her ailing mother about the dire situation in Scotland, she finds herself looking to Francis for aid. Catherine finds herself up against Narcisse as she fights to become the regent to Charles. Meanwhile, Elizabeth faces continued pressure to wed.

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.

As everyone tries to come to terms with Francis' death, new struggles arise for both Mary and queen Catherine for her to be voted regent. New relationships are born and some are starting to tare.

When Prince Don Carlos of Spain visits France, Mary uncovers a dark secret he is hiding and enlists in Catherine to advise her on how to handle. When Gideon, the new ambassador from English court arrives, suspicions arise about what his true intentions are, while Bash's pursuit of the mysterious killer comes to a head at Greer's tavern.

As Mary and Catherine deal with the aftermath of Prince Don Carlos' accident, Mary realizes that she will have to marry for the good of her country and not follow her heart. When Catherine is accused of poisoning Francis, Lola is shocked when Mary thinks Narcisse framed Catherine in order to become Regent of France.

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.

Mary (Adelaide Kane), in order to protect Elizabeth (Rachel Skarsten), unknowingly puts Gideon's (Ben Geurens) life in danger. To save him, Mary turns to another Englishman for help - Robert Dudley (Charlie Carrick). Meanwhile, Bash (Torrance Coombs) is determined to track down the men behind the threats to Catherine (Megan Follows). Anna Popplewell, Craig Parker, Rose Williams, Celina Sinden and Jonathan Keltz also star.

Mary realizes her need to return to Scotland is becoming increasingly imminent and that along with the help of Bash, she must raise her own army to save her throne. Elizabeth enlists Lola's help to find out information about her mother, which backfires when Lola gets caught.

Lola tells Mary she may have a chance to get to Scotland. A murder takes place and Catherine is framed for it. Mary must decide if she should help Catherine or leave for Scotland. If Mary helps Catherine it could eliminate the possibility of safe passage to Scotland.

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.