Teen Wolf's Stiles uncovered a terrifying truth about himself during "Illuminated," a revelation that was made all the more horrifying by the fact that he has no recollection of his actions.

Stiles (Dylan O'Brien) may believe that his hallucinations are over, but purposely - albeit seemingly unconsciously - giving a killer its next victim's name does not seem like the actions of a person who has closed the half-open door in his mind.

'Teen Wolf' Season 3 Spoilers: Stiles Checks Into A Mental Hospital, Dylan O'Brien Tries To Keep Character's 'Confident Energy' [VIDEO]

"It gets worse, for each of us," O'Brien told Collider of his character's continuing problems. "There literally becomes a point where Stiles is going to check himself into a mental hospital. It's that bad. We finally pinpoint what's going on mid-season, but then that just brings on a whole other bag of problems, like how it usually goes on our show."

It looks the Beacon Hills teen will make that promised trip to the hospital during next Monday's "Silverfinger." As the Argents track down a lead and Scott's (Tyler Posey) pack tries to protect Kira (Arden Cho), a worried Stiles will pay a visit to Mrs. McCall (Melissa Ponzio) (see video below).

"It's pretty huge," Ponzio said of the upcoming scene.

'Teen Wolf' Season 3 Spoilers: Scott, Stiles & Allison Not In The Clear, Get 'More Than Their Mojo Back' [VIDEO]

With a major character death looming on the horizon, Holland Roden (Lydia) recently told E! that a "very good friend" will soon be in a "vulnerable position." Could she be referring to Stiles?

Catch Teen Wolf Mondays at 10 p.m. ET on MTV.