Valack and Lydia in “Unfinished Business”

When did you know for sure? That the Dread Doctors had succeeded?

Lydia

[weakly] Scott and Stiles found out that night.

The night of the supermoon.

Lydia

But they really didn't know it yet. There was too much going on. Liam had almost killed Scott. Kira was still gone. Malia was trying to find the Desert Wolf...

You were missing.

Lydia

And Sheriff Stilinski was dying...