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.
Mary is presumed dead, so Elizabeth seeks her crown with assistance from Lola. Meanwhile, Mary's half brother tries to safeguard her throne from John Knox; and Mary and Bash wind up in the clutches of the intimidating clan leader who killed Francis.
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 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.
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.
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 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.
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'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.
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 Mary (Adelaide Kane) and Catherine (Megan Follows) deal with the aftermath of Prince Don Carlos' (guest star Mark Ghanime) 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 (Toby Regbo), Lola (Anna Popplewell) is shocked when Mary thinks Narcisse (Craig Parker) framed Catherine in order to become Regent of France. MORE -LESS
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 realizes she must help Catherine (Megan Follows) 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.
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's mother sends her a pressing message to inform her of Scotland's troubles, so Mary seeks help from Francis. Meanwhile, Narcisse becomes an obstacle in Catherine's endeavor to become the regent to Charles; and pressure mounts for Elizabeth to marry.
King Antoine returns unexpectedly, so Mary helps Francis conceal his deteriorating health in order to save his family's future. As time runs out, they're forced to turn to an unlikely ally.
Catherine is imprisoned when she returns to France, and Elizabeth faces a political backlash for sheltering her. Meanwhile, the fate of Scotland's future forces Mary to make some tough choices; and Lola feels torn regarding Narcisse.
Mary faces struggles in Scotland as Elizabeth and Catherine unite against her. Meanwhile, Elizabeth loses focus because she grows tempted by her first love; and Francis' fate remains uncertain.
