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 unearths a dark secret being kept by a Spanish prince, so she seeks Catherine's counsel. Meanwhile, suspicion surrounds a new ambassador from English court; and Bash's quest to find a mysterious murderer takes him to Greer's tavern.

Mary must marry again in order to help Scotland, whose welfare she has to prioritize over her heart. Meanwhile, Catherine is accused of poisoning Francis, but Mary believes Catherine is being framed by Narcisse, who's angling 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.

Mary's feelings for Gideon are hard to suppress, but she does her best as she seeks political allies. Meanwhile, Elizabeth and Greer face gut-wrenching scenarios; Claude is in danger on her wedding night; and a power struggle over the regency continues.

Charles' coronation nears, forcing Mary to find a suitor who will be her ally. Meanwhile, Lola discovers who's been poisoning Elizabeth; and the castle's serial killer has special plans for Catherine.

Mary must prioritize her life over her cousin's. Meanwhile, Lola and Elizabeth unexpectedly join forces; Catherine can't escape her past; and Mary and Gideon begin to see each other in a new light.

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 realizes she must return to Scotland and raise an army to save her throne; Lola gets caught while trying to help Elizabeth find information about her mother.

Mary learns from Lola that she has a chance to get to Scotland safely, but she must act quietly and quickly. When Catherine 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.

When Mary is presumed dead, Elizabeth asks for Lola's help in taking the Scottish crown for herself; James must defend Mary's throne from John Knox; Mary faces Francis's killer.

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.

Queen Mary, unsure who to trust, tests her brother James to ensure his loyalty after hearing of his meeting with John Knox. Queen Elizabeth agrees to help Lord Darnley, in an attempt to sabotage the powerful suitor’s relationship with Mary.

Queen Mary discovers there is a leak amongst her advisors and sets out to uncover the traitor. Queen Elizabeth enlists Narcisse to further her quest for supremacy. Catherine takes desperate measures to regain some of the power she has lost.

Gideon shows Mary what life could be like if she chose love over country. Catherine fights to cover King Charles' increasingly erratic behavior, while Claude finds an enemy in her sister Leeza.

When Lord Darnley surprises Mary with a visit in Scotland, Mary sees a glimmer of a union that could be more than just political. Elizabeth fights to gain allies in her favor and Catherine must work to get Claude back on track by finding her a new husband.

In order to get Mary to agree to a marriage, Lord Darnley must demonstrate his loyalty when she voices her concerns about his true intentions. Catherine and Narcisse work to repair King Charles' reputation after rumors spread about his strange behavior and threaten the throne.

Mary must deal with the political repercussions of a potential marriage to Lord Darnley and King Charles disappears, leaving Catherine to pick up the pieces. Elizabeth comes to Gideon's aid, while Claude receives an interesting proposition.

When Darnley gets a surprise visitor, his marriage to Mary hangs in the balance. Elizabeth learns her attempt to stop Mary backfired. Meanwhile, Catherine and Narcisse find King Charles and must convince him to return to the castle.

As Mary’s upcoming wedding looms, a terrible tragedy pushes Mary and Darnley apart, forcing Mary to enlist in Catherine’s help. Elizabeth encounters a traitor to Spain, who petitions her to support an expedition to the New World.

Mary and Darnley wed in a lavish affair, which proves to be a successful decision in regards to her political standing. James makes an interesting discovery about Greer, while Elizabeth frantically tries to salvage England’s power.

Mary contemplates how to take over the English throne; Elizabeth struggles to find an appropriate suitor to marry. James gets caught up in a scheme orchestrated by John Knox.

Mary and Darnley are at odds as their plan to seize England is put into action. Elizabeth is conflicted about her feelings for Gideon. Catherine's son Henri tries to claim the throne from Charles.

After a tragic earthquake hits Scotland, Mary must face John Knox amidst claims that she isn't coming to the aid of her people. Elizabeth takes drastic measures after she is discovered with Gideon, while Charles makes a decision that backfires.

Darnley teams up with John Knox to strip Mary of her throne, which will leave a close friend of Mary's dead. Elizabeth must banish Gideon from court at the request of her future husband, while Charles takes a bold stance against his brother Henri.

Mary pursues justice by launching a counterattack on her conspirators. Elizabeth suffers a major setback, and it turns her world upside down.

Mary’s life hangs in the balance — Childbirth threatens to take Mary’s life, which leaves her and her unborn child’s safety in jeopardy. Elizabeth discovers that someone in her inner circle was the cause of the death of someone close to her.

In the series finale, Mary changes the course of history with a decision she makes, and her perilous move for survival causes her to have a stunning realization. Meanwhile, Elizabeth steadies herself for war and becomes the instigator in Mary's demise.