What if they didn’t run? (Spoilers)
When the team discovers the bodies in the woods, Vaughn and Marcus run.
What if Vaughn and Marcus didn’t run?
By running, they 100% revealed that it was them.
What if they had stayed and pretended to be shocked at the bodies?
The family has some hunches that it was them — the way they went out late the night before, and the way Marcus said “they” when he heard the nephew was missing. But those hunches are not enough, right?
Running away is the act that gave them away.