'Reign' Season 1 Episode 18 Spoilers: Mary's Brother Visits, Asks Her to Return to Scotland [Video]

Mary discovered a damaging secret clause in her marriage contract on the latest episode of "Reign."

In "Liege Lord," Lola (Anna Poppelwell) pushes Lord Julien to propose so she can attribute her pregnancy to Julien.

Julien confesses to Lola that he's been married twice before, and that both wives died giving birth, which made him decide not to have any more children. But he tells her that "there are ways to prevent conception."

He then proposes, and Lola accepts.

Charlotte (Amy Groening) pulls Mary (Adelaide Kane) aside to tell her about a clause in her marriage contract with Francis that says Scotland will belong to France if she doesn't produce an heir to the throne before her death. Mary has some well-known fertility issues, and may not be physically capable of having a child.

Francis is furious upon hearing about the secret clause, and wants to see if for himself to confirm that it's real. Mary asks Kenna (Caitlin Stasey) to sneak into the King's chambers and grab the contract.

After Kenna has to endure some forced lovemaking with the King, she successfully delivers the contract to Mary. Mary and Francis begin scheming about how to get Scotland involved to help free her from the binding contract. To get the plan underway, they throw a party for some Scottish aristocracy.

At the party, Mary summons Lord Mackenzie and the rest of his men into a room and asks them if they will deliver the news of the contract to Scotland. She tells them to tell the Protestants that France betrayed them, as it will anger her mother and force her to burn the contract to protect her country. The Scots agree.

Meanwhile, Lola confesses to Julian that she's pregnant with another man's child. Julien is okay with the news, and still wants to go through with the wedding.

Then Queen Catherine (Megan Follows), who bedded a Scotsman after fooling him into thinking that she was a lady-in-waiting, is told by the Scot that they're heading back to Scotland early. This makes Catherine believe something's up, so she goes to the king's chambers and finds the contract missing.

Not long after, men burst into a brothel to slit the throats of Lord MacKenzie and his men, then set the whole place on fire.

One of the killers returns to Catherine to tell her the men are dead. Mary finds out and slaps Catherine across the face. Catherine tells her that she doesn't have time "to calm down two countries."

Mary demands the contract, saying she will tell the world that France is "open for the taking" if Catherine will not give it to her. This scares Catherine into burning the contract.

Adelaide Kane, who plays the show's protagonist, told TVLine that future episodes of the series will see King Henry's (Alan Van Sprang) madness affect Mary.

"Is this an English plot? Is he sick? Has he gone mad with power? He's incredibly dangerous, and no one can put the brakes on him because he's the supreme power in France," Kane said. "And yes, Mary suffers the brunt of his psychosis. He starts getting headaches and hallucinating, and she becomes one of the many targets of his erratic behavior as the season goes on."

There is also the continuing threat of "the Darkness," as well impending civil war in Scotland and France.

Kane also previewed some of the show's upcoming relationship drama.

"Over the next couple of episodes, Kenna and Bash start to come to grips with the fact that they're married, and perhaps they start to see each other in a new light. I think they do try to make it work," Kane said. "Mary and Francis' focus, meanwhile, is on having a child and governing. And Bash isn't the only bone of contention between them. Mary's half-brother James arrives from Scotland, and he tries to convince Mary to return. Naturally, Francis is suspicious of James and wonders if he has ulterior motives in removing Mary from French Court. That causes even more tension between Mary and Francis."

She also said that Mary's French uncle will arrive at court with word of civil unrest, as well as "upsetting news about Mary's mother."

"So Mary and Francis will have to decide whether they can support each other as individuals or sell each other out for their countries," she added.

On the next episode, "No Exit," "Mary's brother visits and asks her to return to Scotland, but Francis is suspicious of his motives. Meanwhile, Penelope takes command as Henry's mental instability progresses; and Lola is skeptical about Julien's marriage proposal."

Watch the promo for "No Exit" below, which airs Thursday, April 17 at 9 p.m. EDT on The CW.