Catching Severus' eye in turn, Jonathan listened intently at what he had to say. Processing it was difficult, but he said it clearly and frankly, which was exactly what he'd asked for. The initial explanation wasn't reacted to beyond a furrowed brow, Jonathan having fallen silent as he mulled it over, considered it, and dealt with the ramifications of what that meant. Only one of them lived. He died. Somehow he died.
And Andrew caused it. He'd done something wrong, something he regretted, and it ended up with him dead and Andrew living until 2004, where he was still grieving enough to tap into a supernatural power that swapped their places. Which meant that Andrew was possibly dead right now. In some kind of limbo or afterlife. Maybe some place bad because of whatever he did to cause the death to begin with...
It was harrowing. Unsettling. He was supposed to be dead, but was alive, here, in a world where apparently something big was happening and Andrew should be here instead. Because this was something that needed to be repaired and undone.
After a time Jonathan's eyes averted from the both of them as it all sank in. There were no tears, no theatrics, nothing. Just a concerned look of both understanding and momentary curiosity as he looked up and addressed Anna, figuring she might now. "Andrew always liked filming and recording things. Since he's not here, maybe he documented what happened. Explained it somehow. I mean, if we're talking logically here... if you guys manage to undo what's happened, Andrew will come back and I'll go back home. Or be dead somehow. So I mean, if he didn't tell either of you what happened, that's the safest bet of figuring it out."
Maybe it was shock. Maybe it was the fact that he was in a good place, a place where he felt confident enough to say that he'd almost done everything he'd wanted. Apart from making up his misdeeds to Buffy and her friends, otherwise he'd lived a pretty good life. Buffy talked him out of killing himself, he went into therapy, met Andrew, met Warren... he'd made friends and lived a pretty solid existence for a while. Minus when he made himself the most important person in the world with a spell. Another thing he always meant to make up to Buffy and everyone else.
Or maybe it was just shock. All Jonathan knew was that he wanted to know how it happened and how he could fix this. But he needed the story if he was going to fix it.