Details about how to beat the Beast will be revealed in the next episode of "Teen Wolf" season 5.

In the trailer for the upcoming episode titled "Maid of Gevaudan," the story about how a young woman named Marie-Jeanne Valet defeated the Beast in France back in the 1700s is shown.

The trailer also shows the return of Crystal Reed in the series. However, she will not portray the role of Allison Argent in the episode. Instead, she will play the role of the legendary Marie-Jeanne Valet, one of the first members of the Argent family line.

In a phone interview with Buzzfeed News, executive producer Jeff Davis revealed how Marie-Jeanne Valet defeated the biggest enemy of the Beacon Hills wolf pack..

""She was a peasant girl who had fashioned a bayonet onto a spear and was supposedly one of the first to survive an attack by the beast," Davis said.

He also mentioned that Allison's grandfather Gerard (Michael Hogan) was the one who shared Marie-Jeanne's story to Scott's pack because he believes that it could help the pack in finding out how to defeat the enemy.

Reed toldBuzzFeed that even if she already announced that she has no interested in reprising her role as Allison after leaving the show during the third season finale, fans of the character will still see a glimpse of her old character in episode 18 of "Teen Wolf" season 5.

"She shares that basic, intrinsic quality Allison had that was just pure kindness. She's fighting for justice and for what's right, and that's something I think they have in common that people will love," the actress revealed.

Aside from Reed, the episode will also show "Switched at Birth" alum Gilles Marini and "The Young and the Restless" star Lachlan Buchanan.

Marini will portray the role of a French soldier named Sebastien, whose sister was victimized by the Beast in the 1700s. Meanwhile, Buchanan will play Henri, a "wise but guarded" member of the Argent family who opted to live alone in the forest.

"Teen Wolf" season 5 episode 18 airs Monday, Feb. 23, on MTV.