"Isn't it a common investigate technique, to first find out what connects the victims? I know nearly everyone here, and I make a point of knowing all their stories¹. Aziraphale himself is a rare books dealer. It's a perfect combination of skills." Which is rather pleasing for Claudius to discover, after remarking on his own uselessness. Nightingale knows investigations, Aziraphale knows books, and Claudius knows everyone's business. "We'll seek him out on the morrow. Take thy rest, Nightingale."

¹ Except SecUnit, he couldn't tell you what's up with SecUnit. Security Consultant, tall, brusque, that's all of it. And Gu Xiang might've been a strange vision brought on by a blood loss.