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.

Mary and Francis take drastic action in response to Henry's madness. Meanwhile, a terror in the woods puts everyone in peril; and Mary makes a bold choice when she discovers Lola is in the midst of a life-threatening labor.

Mary and Francis are taken hostage when the castle falls under siege, and Catherine makes a shocking suggestion in an effort to save them. Meanwhile, Diane reveals to Bash that she's plotting to have him declared legitimate.

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.

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 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.

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.

Nostradamus shares with Mary his prophecy about a death, which leads Mary to make a big decision concerning Francis. Meanwhile, Clarissa gets brazen as she pursues her goals; and Kenna tells Catherine about Diane's intentions regarding Bash.

Mary and Bass return to the castle, where Catherine remains resolved to keep Francis safe from Mary. Meanwhile, Francis learns of the dark prophecy, but it does not dissuade his desire to marry Mary.

Mary must decide whether to marry Bash or Francis, who returns accompanied by Lola. Meanwhile, Mary's mother visits and pushes her own agenda, and her mere presence in the castle troubles both Henry and Catherine.

Mary uncovers her marriage contract's secret clause, which was added by Catherine and her mother, so she and Francis attempt to persuade the people of Scotland to renounce her mother.

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 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.

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.

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.

Mary has a chance to get out of her engagement, but it requires lying and sentencing a man to death. Meanwhile, Francis and Bash suspect that Tomas may be disguising his real motives.

Henry claims Catherine has committed treason and adultery, so she attempts to save herself by shedding light on a dark part of Bash's past, and Bash and Mary then try to even the score. Meanwhile, Nostradamus discloses the truth about the castle's ghost.

Bash saves Francis' life while they're in the woods exploring the latest ominous threat. Meanwhile, Henry becomes obsessed with a servant who won a contest; Greer is seen kissing a kitchen servant; and Henry forces a new couple into a union.

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.

A Portuguese prince offers much-needed aid to Scotland if Mary accepts his marriage proposal and break things off with Francis. Elsewhere, Francis' feelings for Mary lead him to put Bash in a risky situation.

Mary's honeymoon ends and she returns to the castle. Meanwhile, Lola displays some odd behavior, which leads to a secret being exposed; Bash finds a bewildered Olivia and asks Nostradamus to assist her; and Henry seeks help from Catherine.

Mary hires a mercenary to help her save Scotland. Meanwhile, Francis prepares France to wage war on England, and Leith becomes his ally in this endeavor; and Lola and Julien's bond deepens, but she fears he will betray her.

Mary teams up with Catherine to deal with Henry, whose deranged behavior puts Francis at risk. Elsewhere, Bash resolves to destroy the Darkness after meeting a boy who survived the horror; and a devoted Lola tries to protect Julien.