"Hallo, what are you doing up so late?"
"Researching my next monograph." He cracked open a prodigious volume and blew dust from the yellowed pages; like sand it fled from his breath. "It will be my most exhaustive yet; I'll be staying up all the night, and I don't expect to do more than scratch the surface."
"Speaking of things exhaustive—I'm afraid I can't keep you company this time," I said through a yawn. "I'll be heading upstairs in just a moment. Hope you don't mind."
"That's quite all right, Watson; I'll do better with—"
"Hm? With what?" I turned curiously in his direction, just in time to see the tail end of a yawn.
"Excuse me. I was going say, without distractions. I appreciate your company, but sometimes the mind works best alone."
"Oh, yes. That makes sense," I agreed sleepily.
"Stop that!"
"Stop what?" I blinked.
"Stop yawning! You're going make me—"
I laughed softly; he could not even keep his eyes open for this yawn. "Sorry, Holmes."
He cleared his throat and refocused on the text. "There's nothing to be sorry for; you're tired, you should get some sleep. I'll just—"
"Good heavens, Holmes, you nearly unhinged your jaw there!"
He threw the book across the room. "Confound it all! I'm going to bed!"