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.