Scott and Stiles in “Unfinished Business”

Scott

So, Boyd and Cora might not have killed anyone?

Stiles

[sighs] You're gonna wish they did.

Scott

Why?

Stiles

I'm not exactly sure yet. The other girl who was out in the woods, Emily? Eventually, they're going to find her. She's one of them. Emily, Heather, that guy Lydia found at the pool? All three were virgins. And they're all gonna have the same three injuries-- strangled, throat-slashed, head bashed in. It's called the three-fold death.

Scott

[stunned] So, if these aren't random killings, then what are they?

Stiles

Sacrifices. Human sacrifices.