The following contains spoilers for Wednesday Season 1, now streaming on Netflix.

When Wednesday announced the addition of Christina Ricci to its cast, it set fans buzzing. The actor made an indelible mark as Wednesday Addams in 1991's The Addams Family and 1993's Addams Family Values -- performances that rocketed her to stardom before the age of 14. Her arrival on the new series immediately felt like a fitting homage, as well as letting her give her blessing to the show's new Wednesday, Jenna Ortega.

As it turns out, the show has much more in mind for her than simply making a cameo. Christina Ricci's character, Marilyn Thornhill, plays a major role in the series' first season, and even as Ortega basks in well-earned praise for her singular and impressive take on the title character, so too has Ricci collected her share of accolades for her own work on the show. Thornhill is a long way from Wednesday, but her part in the series may be just as important. Here's a breakdown of who she is and why she's so vital to Wednesday's first season.

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Marylin Thornhill Is Nevermore's Resident "Normie"

Christina Ricci as Ms. Thornhill in Netflix's Wednesday.

Thornhill first arrives to welcome Wednesday when she's first sent to Nevermore Academy in Season 1, Episode 1, "Wednesday's Child Is Full of Woe." As the designated "dorm mom," she admonishes Wednesday to reach out if she needs any support. Wednesday responds to the offer with skepticism -- the same as she does with everyone else at Nevermore -- but slowly, grudgingly warms to the teacher's entreaties.

Her field of expertise may have helped on that front. Thornhill teaches botany, with an emphasis on carnivorous plants -- a subtle hint of things to come -- as well as a reason for Wednesday to respond positively to her. She's also the school's only "normie" instructor, meaning she possesses no supernatural powers and doesn't belong to a species like gorgons or werewolves. Her friendliness towards Wednesday appears genuine for most of the first season. The finale, however, reveals a very different side to her, and a shocking answer to Wednesday's biggest mystery.

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Thornhill Is the Secret Foe of Nevermore

Christina Ricci in Wednesday

Throughout the first season, a monster called a "Hyde" has been murdering people in the woods near the school. Wednesday diligently searches for the culprit, only to learn that she's been played for a fool the whole time. Thornhill actually controls the Hyde, and has been using it to prepare for a long-awaited act of revenge against both Nevermore and the Addams Family themselves. Her real name is Laurel Gates, the last survivor of a local family who hates the "outsider" inhabitants of the academy. Thirty years ago, her brother was killed after trying to poison the school's Rave'N dance, and attacking a young Gomez Addams in a jealous rage.

Laurel responds by faking her death, and inserting herself into Nevermore's community, until the rise of the blood moon lets her enact her plan. Using Wednesday as a sacrifice, she resurrects the corpse of Joseph Crackstone, the puritanical founder of the nearby town who dedicated his life to hunting down outsiders like the kind at the school. She sets him loose on Nevermore before Wednesday rallies, taking the both of them down with a little help from her school friends.

Her final fate is unknown. Wednesday knocks her unconscious at the end of Season 1, Episode 8, "A Murder of Woes," likely leaving her for the authorities. But by then Laurel has proven herself a formidable foe to both Wednesday and the other adults in the story: coming within a hair's breadth of destroying them all while smiling to their faces the whole time. Small wonder that they let the woman who used to play Wednesday square off against the new model.

The first season of Wednesday is currently streaming on Netflix.