Derek shares a moment in this Teen Wolf scene. It is from the episode "The Overlooked."
The boys are trapped in a hospital during a storm on Teen Wolf. "The Overlooked" is the tenth episode of the show's third season.

Teen Wolf Season 3 Episode 10 Quotes

Melissa: You're him, aren't you.
Deucalion: Him?
Melissa: The bad guy.
Deucalion: You have no idea.

Melissa: You're supposed to be dead.
Peter: I get that a lot, actually.