VIDEO: Sneak Peek - 'No Exit' on Tonight's REIGN on The CW

On tonight's episode The CW's REIGN titled "No Exit", when Mary's brother James (guest star Joe Doyle) arrives in France and convinces Mary to return to Scotland, Francis (Toby Regbo) is suspicious and uncovers a plot that would destroy Mary (Adelaide Kane), which causes a rift between them. King Henry's (Alan Van Sprang) downward spiral continues, leaving Penelope (guest star Kathryn Prescott) in charge, causing Catherine (Megan Follows) and Kenna (Caitlin Stasey) to take drastic measures. Meanwhile, Lola (Anna Popplewell) becomes wary of Lord Julien's (guest star Giacomo Gianniotti) motives behind his marriage proposal. Torrance Coombs and Celina Sinden also star. The episode was directed by Mike Rohl and written by Hannah Schneider 

The episode airs Thursday, April 17th, (9:00-10:00 p.m. ET) on The CW. Get a sneak peek below!

In the lines of the history books is the story of Mary Stuart, the young woman the world would come to know as Mary, Queen of Scots. The teenage Mary is already a headstrong monarch ? beautiful, passionate and poised at the very beginning of her tumultuous rise to power.

Arriving in France with four close friends as her ladies-in-waiting, Mary has been sent to secure Scotland's strategic alliance by formalizing her arranged engagement to the French king's dashing son, Prince Francis. But the match isn't signed and sealed, it depends more on politics, religion and secret agendas than affairs of the heart. Prince Francis is intrigued by the fiery Scot, but like most young men, he resists the idea of settling down into marriage, especially when he has a history with a lady of the court and his own point of view on the wisdom of an alliance with Scotland. Still, an attraction between Mary and Francis is ignited.

Further complicating things is Bash, Francis' handsome, roguish half-brother, who has a history of his own despite his illegitimate birth, Bash is his father's favorite. Though he is all too aware that Francis is the heir to the throne and Mary's intended, Bash soon develops his own feelings for Mary. None of the intrigue at Court is lost on Francis' mother, Queen Catherine. The strong-willed Queen is aware of Mary's inflammatory effect on her son and his half-brother, just as she is aware of the dalliances of her husband, King Henry, not only with his mistress, but with other ladies of the Court, as well. For guidance, Queen Catherine turns to her trusted advisor, the seer Nostradamus, who terrifies the Queen with his prophecy that marriage to Mary will cost Francis his life. Catherine is determined to save her son, no matter how many others have to pay with their lives.