Magnus Bane is not himself in this week's episode of Shadowhunters. No, he's really not himself. In fact, he's Valentine Morgenstern, or at least he's in the bad guy's body after an unfortunate run-in with a greater demon in the previous episode.

That's right: Magnus (Harry Shum Jr.) is now trapped in Valentine's (Alan Van Sprang) body, which means he's the one currently imprisoned by The Clave in the Institute, not Valentine. While poor Magnus is being tortured in tonight's gripping episode ("You Are Not Your Own"), Valentine learns that being a "filthy" warlock isn't so bad, especially when there's magic involved. But first he has to learn what to do with those hands.

"There's a certain grace to Magnus, but with Valentine, every movement is calculated," Shum told MTV News ahead of the episode. "And there's a real frustration in Valentine not having full control for the first time."

"As an actor, you get this challenge to play someone outside of who you've been playing for the past two seasons, and it's a real treat, especially someone like Valentine," he added. "He's such a complicated character. It wasn't really about mimicking him — it was also about what he would act like if he was not trying to let anyone know he was this person in someone else's body."

The harrowing experience is going to leave the immortal High Warlock of Brooklyn with lingering trauma, as he'll be forced to confront painful memories from his past — some not voluntarily. He'll also be confronted with a choice to "completely turn his back" on The Clave.

"The body-swap alone is very invasive. It's a violation of someone's body," Shum said. "It's interesting and fun to watch, but when you think about it, if someone went into your body and you don't know what they did during that time, it can cause lasting damage to someone. It can also bring out things from the past, things that they've suppressed for a long time for good reasons."

Obviously, this means Magnus will lean on Alec (Matthew Daddario) for support, but with Shadowhunters dropping like flies, and a group of Downworlders who want justice following Valentine's massacre at the Institute, Alec may not be as emotionally available as Magnus needs right now. But the long-awaited arrival of Sebastian Verlac (Will Tudor), a Shadowhunter from the London Institute, might just put everyone on edge.

"Magnus is just starting to trust Shadowhunters, but he still doesn't really trust any of them," Shum said. "So bringing someone new, especially from London, given his past, he's very cautious. The question is whether he wants to even get involved. His loyalty ultimately lies with his people and the Downworlders."

Given the torture he endures at the hand of The Clave in this episode, we really can't blame him.