Aziraphale knew something was seriously wrong when he found Crowley getting very drunk in his flat. Alone. Crowley *never* did that. He knew all about alcoholism, he'd helped create it.
"Crowley? What is it?"
"Just keep thinking about Loki. I knew him, you know? Before the Fall. I looked in on him and Bartleby every so often, when I was in America. Poor bastard. Wisconsin must have driven them both crazy…"
"It was their just punishment, you know that, Crow-"
"You don't understand! Bartleby killed him! Six. Thousand. Years. And then he killed him. You don't get it, do you? They'd been together as long as we have…"
"Oh, Crowley. You don't really think that will ever be us? As you said, they were being punished. Bartleby must have gone insane".
"I know. But there but for the grace, angel. There but for the grace".