Mary (Adelaide Kane) plots to steal Elizabeth's (Rachel Skarsten) throne in the upcoming episode of "Reign" season 4.

Titled "A Better Man," the show's 10th episode will see Elizabeth feel more threatened with her cousin. According to the official synopsis, Mary seeks help from different sources as she strategizes new ways to steal the English throne. Now that Mary is married, Elizabeth thinks that time is running out and she must find an appropriate suitor to marry soon. Elsewhere, James (Dan Jeannotte) gets involved in a scheme made by John (Jonathan Goad) and is forced to deal with its tragic results.

The CW released a new sneak peek for the episode. It opens with Mary declaring her plans to take over England. The next scene cuts to Darnley (Will Kemp) asking Mary if he could visit her chambers in the evening. The clip also hints that there's a plot against Mary's life, which forces her to leave the castle for her safety. "We're one step closer to civil war," Catherine (Megan Follows) warns a mystery character at the end of the teaser.

In the previous episode, "Pulling Strings," Bothwell (Adam Croasdell) kissed Mary and tried to convince her to marry him instead. She refused to take his offer because she is already pregnant with Darnley's baby. Darnley sought the help of Cardinal Odomo (Paulino Nunes) to usurp the Queen of Scots' power, but he was eventually caught by Mary, thanks to Catherine, James and David's (Andrew Shaver) help.

Martin (Saamer Usmani) went to Scotland for the big wedding and was able to spend time with Rose (Ali Lyons). As James grew closer to Greer (Celina Sinden), he found out that Martin is Rose's father. Mary and Darnley still tied the knot, while Elizabeth was shocked when some Catholic border towns switched from English and Scottish as a sign of support for the newlyweds. Gideon (Ben Geurens) comforted Elizabeth and they ended up being intimate with each other.

The fourth and final season of "Reign" airs every Friday night at 9 p.m. EDT on The CW.