It's right there in front of him, he can feel the curvature when he slides his hand just a little—
With a choked-off scream, and inhuman force and speed, he lunges at the wall behind him. The fact that he bounces back onto the floor doesn't seem to deter him in the slightest. Nor does the fact that his second attempt breaks all the fingers on his right hand. After that, he's moving too fast too constantly for the extent of the damage to be visible, and the screaming hits maximum volume about half a second in and doesn't get much more informative from there.
If anyone watching had the visual processing speed necessary to see him clearly, they would notice his movements becoming less desperate and more mechanical over the course of the next few seconds. He stops rebounding all over the inside of the ward and begins concentrating on a single narrow arc facing away from everyone else in the room - then on a single spot within that arc, chest-height on him if he were standing still, if he were capable of standing still right now - and finally, at the end of four or five seconds from the moment Keo started working at him, he ceases screaming abruptly and drops to the floor like a marionette whose strings have just been vaporized.
Most of the bones in his hands, wrists, and forearms are broken at least once each. His feet have fared better only because he was wearing shoes.
"Debatably," he says. His voice is rather hoarse, but still intelligible. "Nice trick."
"Mnh. Don't care," he says. "It's useful. Reminds me not to move." And he is indeed hardly moving. "What are the conditions that'll get me let out of here? And optionally some medical care? I can put myself back together from here without help but it'd be a brutal job and I'd rather not have to."
"I have to be convinced that you're not going to be a danger or a liability, at least not more than balances against the inconvenience of looking after while you're in there. I can find that out to my satisfaction with the fancy mind tricks if you like. If I let you out, you can see a light about your injuries; I'd have to check the exact spell the girls used to say whether one will be able to work through this kind of ward or not."
"Sounds convenient. What are your fancy mind tricks going to tell you about my danger levels?"
He is telling the truth on both counts. He's willing to break laws that interfere with his survival, or that are so pointless and unenforceable it's not worth it to comply, but strongly prefers to avoid trouble otherwise; he has a similar approach to violence, and has been receiving a strong impression that he is far enough away from home not to have to worry about the major threat likely to incite violence from him in the name of survival.
There is the matter of what happens when you lock him in an enclosed space with no way to leave, but that's an extremely specific situation and, as proven here, more likely to hurt him than anyone else. It would be dangerous to enclose him in a ward and then get in there with him; he has worked on this problem enough that, contrary to his overcautious warning to the children, in the heat of the moment when rational decisionmaking is beyond him he will choose escape over causing harm whenever both are available.
That's doable. Not pleasantly, but doable. He moves his hand the absolute minimum amount required to touch hers.
"Oh my goodness! Stars and planets, oh my goodness!" She cups her hands together and makes a bubblegum-pink ball of sparks, which she presses to the nearest available extremity of the visitor.
He smiles and sits up, rolling his shoulders and opening and closing his hands to check functionality.
"Nice trick," he remarks. "The kid mentioned sending somebody like this to cover for my job?"
"I fix injured people. Not as efficiently as this, but more efficiently than pretty much anyone else whose job it is to fix injured people."
"They wouldn't handle it well, but they'd handle it. If I'm going to be here for months I'd rather they had an explanation and the explanation might as well come with a stand-in."