A threat

As soon as you make even the tiniest of moves, the man steps over and grabs Natasha by the arms, yanking them behind her back.

"Don't you fucking dare resist." He warns, sternly. "You know how it is. Do as I say, and I'll be careful. Do anything stupid, and the only one that suffers is your friend here."

He mimes how easy it would be for him to yank Natasha's arms up high behind her back, causing her serious amounts of pain.