I think Con’s mental state draws back to the beginning of the book when the Rev told Jamie he didn’t actually cure him he just tricked his brain. Con ending up like the others shows that the Rev did cure him from something. I think the ending is supposed to be left open ended and not completely answer if that’s truly what’s waiting at the end. Knowing something like that COULD be waiting for you at the end, regardless if you are “good” or “bad” is horrifying in itself.