Queen Mary struggles to hold on to her power in Scotland amidst Queen Elizabeth's campaign to sabotage her with the help of a new ally in Queen Catherine. Meanwhile, with Francis' fate at odds and Elizabeth distracted by temptation in her first love, Robert Dudley, both queens struggle to rule.
Elizabeth must deal with the political backlash of harboring Catherine in England, while Catherine is imprisoned upon her return to France. Mary is forced to make some difficult decisions about securing Scotland's future and Lola is conflicted in her feelings for Narcisse.
When King Antoine unexpectedly returns to Court, Mary must help Francis hide his weakening condition long enough to secure his family's future. With the Throne in jeopardy and time running out, they must turn to an unlikely ally in need of redemption.
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.
Grateful for a future with a revived Francis, Mary considers signing away her claim to the English throne, and staying in France forever. Catherine learns that Nostradamus has returned -- with a new vision involving Francis' fate.
Mary realizes she must help Catherine in her quest to become regent, even at the risk of hurting the alliance with Scotland. Claude is determined to help Leith marry while Elizabeth struggles with the prospect of losing Dudley.
Mary, in order to protect Elizabeth, unknowingly puts Gideon’s life in danger. To save him, Mary turns to another Englishman for help – Robert Dudley. Meanwhile, Bash is determined to track down the men behind the threats to Catherine
Mary (Adelaide Kane) learns from Lola (Anna Popplewell) that she has a chance to get to Scotland safely, but she must act quietly and quickly. When Catherine (Megan Follows) is framed for murder, Mary must decide if she should stay to protect her, which would jeopardize her safe passage to Scotland.
When Mary arrives in Scotland, she is stunned by the treacherous world it has become and is forced her to keep her royal identity a secret until she learns who she can trust. When Elizabeth jeopardizes her standing with an unbearable new suitor, Lola steps in to help, which causes the Queen to question Lola’s ulterior motives.
Mary makes a bold move to defend her reign in Scotland, which results in a battle royale with her cousin, Elizabeth. Lola is accused of a heinous crime and suffers the drastic consequences. Meanwhile, back in France, Catherine finds that Charles has returned a changed man after paying a price for his mother's relentless quest for power.