The doorbell rang and since Mrs. Hudson was away for the weekend Dr. Watson answered the door.
When he opened the door, he saw a schoolgirl standing before him. “May I help you?” he asked the young lady.
“Sir, I’m here to see Sherlock Holmes,” she replied.
The good doctor showed her to Holmes’ study and quietly closed the door as he left the room.
A few minutes later, Watson heard what appeared to be the sounds of a great struggle coming from the room. Watson concluded that the evil Professor Moriarty had been cleverly disguised as the schoolgirl and was doing away with the great detective!
Bounding across the room, Watson burst through the door only to see a naked Holmes lying atop the schoolgirl.
Shocked by the display, the good doctor sputtered, “I say, Holmes, just what sort of a schoolgirl is this?”
Holmes looked up and calmly replied, “Elementary, my dear Watson.”