Grif catches Victor's slap more because he's fast and wired to the gills on adrenaline than because he's any good at defending himself. He's almost as surprised by his own success as he is by the smack.

"How did you get here?!"

Okay, that's not an answer. Slow down. Inhale. He grabs Victor's arm and starts pulling him, not running yet but if you'd just give him a second to work up to it-

"We gotta get out of here before it finishes- before it closes-" he can't decide, "Before it does whatever it's doing!"

Because he may not know why the halls keep getting shorter but it's for a bad reason.