Holmes and Watson are camping out on Dartmoor, still chasing the Hound of the Baskervilles, when Holmes says to Watson, "Are you asleep?"
Watson replies, "No Holmes, on such a beautiful starlit night as this, I'm happy to be awake."
"What does that tell you?" Holmes asked.
"That the weather is fine."
"And?"
"The skies on Dartmoor are clearer than the London smog."
"And?"
"I don't know what else to add, Holmes."
"How about, some bastard has stolen our tent?"