The explanation comes to him in a buzz. Leo tries to shake his head, say he doesn't care if Donnie can't heal him, but it makes his vision swim a little so he stills. Honestly, it doesn't really matter; whatever Donnie's up to, Leo trusts him.

...Up until the moment the words wait here fully register.

Leo panics, grabbing his brother's arm. No, no, where is he going!? He can't go off on his own, it's not safe!

(He can't leave me here alone!)

It's that thought that gets Leo to drop Donnie's arm again, abruptly. No, he can't be like that. He can't show fear. He has to be strong.

"...Sure," he says, finally, and it sounds like it takes the wind out of him.