He's surprised, that much flickers through. He recognises the box, they all would, and for a moment he feels utterly furious with the Doctor for allowing this to happen to River. He's surprising even himself, this fierce protective urge. But then again River understands him, understands Erik. She was the first person to make them both relax and he cares for her deeply.

So the first thing he attempts is to strengthen the barrier, to cushion the impact as much as he can. It isn't going to be enough but it might stop it hurting while he figures out how to get rid of it.