"Look, Watson," said Holmes, "this is really quite simple. The doorknob is wet, and Lord Thornberry has a dreaded fear of water, but his butler knows this, and is currently under arrest and not talking. But what everyone has failed to take into account is that the butler is a deaf-mute, who is immensely faithful to Lord Thornberry. The doorknob is not covered in water, but in sweat, from the butler's nervously perspiring hands. It couldn't be the wet doorknob that put Lord Thornberry into a coma -- but then what did, and where's the maid?"
"I'll tell you," said Lord Thornberry. Everybody fainted. "Well, when you wake up anyway."
But nobody woke up until the next morning, when Holmes had left. As a result the mystery remained until the Tooth Fairy revealed all. It was the maid (Watson's wife) who did it. But what did she do?
"All I know is that she walked in with a wrench when Lord Thornberry
was conscious, and when she walked out, he was unconscious." Go figure.
"It wasn't her fault," said Lord Thornberry, "she just put some water
in my tea."
"Oh. OK, then."
Everyone left, satisfied.