Wednesday ending explains who was controlling the Hyde monster and who blew up the cave
Wednesday ending explains who was controlling the Hyde monster and who blew up the cave( Source : dmtalkies )

Marilyn Thornhill blew up the cave in the show Wednesday. Marilyn had kept Tyler in the cave while she transformed him into Hyde mosnter.

Episode eight opens up with Wednesday knowing Tyler about being a hyde, which he refuses. The final episode sets up a potential season 2 and unveils the villain with many questions still needing answers.

The final episodes saw Wednesday dealing with the aftermath of her understanding from the previous episode. It reveals that Tyler, who spent most of the season as her love interest, is the same monster she's been hunting.

Eugene Witnessed A Person With Brown Boots Blew The Cave

Eugene reveals Wednesday that he saw someone wearing red boots blow up the Hyde cave. That person is Marilyn Thornhill, aka Laurel gates.

In the final episode, Wednesday visits Eugene to say goodbye after he wakes up from his coma. During the visit, Wednesday realizes Marilyn is the protagonist.

Previously Xavier had made a painting of Hyde standing in that cave. Eugene soon recognized the cave and took Wednesday there. Then they realized that it was the Hyde Monster's lair, as bones of other animals were lying there.

It was the cave where Marilyn Thornhill had kept Tyler in the start when he was going through the transformation. There he was handcuffed and injected with chemicals to be Marilyn's slave.

Eugene recalls seeing a figure at the monster's cave who wore red boots, matching Ms. Thornhill's.
Eugene recalls seeing a figure at the monster's cave who wore red boots, matching Ms. Thornhill's. ( Source : menshealth )

Wednesday and Eugene were not attending the Rave'N, so they agreed to search the cave and identify the creature. However, Thing wanted Wednesday and Tyler to go for the Rave'N, so he set them up very cleverly.

As Eugene was ready, he realized Wednesday was going to the Rave"N. She asked him not to go to the forest alone, but he didn't listen. He then went near the cave and was attacked by the Hyde monster.

During the attack, he saw a figure at the monster's cave wearing red boots -matching Ms. Thornhill's. After hearing from Eugene, Wednesday quickly learns that Thornhill was behind it. 

Why Did Marilyn Thornhill Destroy The Cave?

Sitting in his hospital bed, Eugene recalls seeing someone wearing red boots before the Hyde cave burst into flames.

It was Marilyn Thornhill who blew up the cave where she had kept Tyler when he was going through the transformation. Wednesday soon realizes that Marilyn was behind it and she was actually Laurel Gates.

She confronts Marilyn with Principal Weems disguised as Tyler. The two get Marilyn to confess her real identity -Laurel Gates. However, she manages to kill Weems and abducts Wednesday.

Marilyn reveals that she used to inject chemicals to control Tyler and has been using him to collect body parts to resurrect Joseph Crackstone. She did so, to use Tyler as her slave.

At the end, Wednesday Addams cracks the case. It is uncovered that Nevermore teacher Marilyn Thornhill is actually Laurel Gates -a descendant of Joseph Crackstone.
At the end, Wednesday Addams cracks the case. It is uncovered that Nevermore teacher Marilyn Thornhill is actually Laurel Gates -a descendant of Joseph Crackstone. ( Source : variety )

Using Wednesday's blood, Thornhill brings Crackstone back. He then stabs her and sets out to murder all the outcasts. Luckily, Wednesday's ancestor Goody Addams' spirit appears to save her life.

With Wednesday's bestie, Enis, having finally transformed into a werewolf form, she defeats Tyler in his monster form. With help from Bianca, Wednesday ultimately destroys Cracktone while Eugene helps in defeating Gates.

In the end, Tyler aka Hyde is detained, Xavier is released from prison, and Wednesday departs Nevermore Academy, Jericho, Vermont, which is closing for the remainder of the semester.