Teen Wolf, Season 5

[Stiles and Lydia are arguing about Dr. Valack's request]

Stiles:
No way. Not happening. Sorry.

Lydia:
He's the only one who knows anything!

Stiles:
The guy is a nut-job who drilled a hole into his head! He's probably lying his ass off!

Dr. Valack:
[frustrated] How many have died so far? All of them teenagers. Am I right? Want to know how many died the first time they came here? Wonder how many will die if they succeed?

Lydia:
[shocked] This did happen before.

Dr. Valack:
And now they're back. All because a few teenagers, who never even considered the consequences, decided to reignite a supernatural force they barely understand.

Lydia:
The Nemeton.

Stiles:
How do you even know about that?

[Dr. Valack removes the bandage around his forehead]

Dr. Valack:
I know because I saw it!