Season 4

After spending a childhood safely hidden away in a monastery, a teenage Mary Stuart arrives in France where she has been sent to secure Scotland's strategic alliance by formalizing her arranged engagement to the French King's dashing son, Prince Francis. Further complicating things is Bash, Francis' handsome, roguish half-brother and Francis' mother, Queen Catherine. When the strong-willed Queen learns of a prophecy that marriage to Mary will cost Francis his life, she is determined to save her son, no matter how many others have to pay with their lives.

When Simon, and English envoy, tells Mary that the English are aware of her fragile engagement to Francis, Mary and Francis put on a show to protect their alliance. Meanwhile, when Queen Catherine learns that someone knows about her plot to destroy Mary is still alive, she stops at nothing to make sure they are silenced for good. Torrance Coombs, Alan Van Sprang, Anna Popplewell, Celina Sinden, Caitlin Stasey and Janessa Grant also star.

When England's armies threaten Scotland's borders, Mary asks King Henry for help, but he refuses. Tomas, the son of the King of Portugal, proposes marriage to Mary, promising her aid against England if she'll abandon Francis and turn to Tomas instead. Francis puts Bash in jeopardy when he lets his feelings for Mary cloud his judgement.

Mary has to decide if she's willing to lie and sentence a man to death in order to have King Henry let her out of her engagement to Prince Francis. Meanwhile, Francis and Bash are suspicious of Tomas' true intentions which will ultimately lead to a confrontation with disastrous results.

When Olivia, who is an ex-lover of Francis', arrives at the castle, she brings the dangers of the woods with her. Mary seeks comfort in Bash. Bash is threatened by heretics for interfering with a sacred blood rite. Meanwhile, Aylee is forced to spy on Mary when Queen Catherine blackmails her.

An attempt to scare Mary causes Queen Catherine to take drastic measures to make sure the guilty party is caught. Francis, aware of Bash and Mary's growing attraction, turns to Olivia. Bash ventures into the woods to pay his debt - the human sacrifice the pagans demand - and returns with blood on his hands. Meanwhile, Kenna comes clean with the girls about her affair with the King, to a mixed response. Jenessa Grant, Anna Popplewell and Celina Sinden also star.