At this point, there is nothing that Crowley could potentially do or say to keep Aziraphale from being worried. Actually, no, that isn’t quite right. There was nothing that Crowley could have said or done to keep Aziraphale from being worried from the moment that Aziraphale had watched him vanish into thin air.

That’s something that is going to stick with him for quite a bit of time, a heavy weight settled underneath his ribs. Just as he imagines that the idea of being replaced will stick with Crowley. It seems so pointless for him to attempt to side-step it. Just something he saw?

No, there must be more than that.

“What exactly did you see? Whom was it that replaced you?” Aziraphale presses, still wearing that same worried frown. He tries not to think about Crowley's reddening face and the sudden wild look in his eye. He hopes he hadn't made a misstep. The only relief is that he hadn't pulled away from him yet, so Aziraphale is determined to keep them both on topic in the meanwhile. It's easier if they don't address this part.

“I want to know everything that happened.”