what is umqra?
When Sherlock, John, and Henry went out at night to look for the hound, John saw flashing lights. He wrote the pattern of flashes down, believing it to be a message in Morse code.
If read as Morse dots and dashes, the flashing lights spelled out “UMQRA.” John thought this might be a clue that related to the mystery of the hound.
When he investigated the source of the flashing lights later, though, John discovered that it had never really been Morse code. It was just random flashes of headlights caused by people who were dogging.
Do you think U.M.Q.R.A meant anything in the Hounds of Baskerville? Will it come back to haunt us?
I think we’ve seen the last of UMQRA. The letters turned out to be a random, meaningless coincidence.
Additionally, the whole idea of John seeing a signal sent with light at night was inspired by a similar situation in the book The Hounds of Baskerville was based on. It’s tied to that specific story.
"I was doing no harm, sir. I was holding a candle to the window."
"And why were you holding a candle to the window?"
"Don’t ask me, Sir Henry—don’t ask me! I give you my word, sir, that it is not my secret, and that I cannot tell it. If it concerned no one but myself I would not try to keep it from you."
A sudden idea occurred to me, and I took the candle from the trembling hand of the butler.
"He must have been holding it as a signal," said I. "Let us see if there is any answer." I held it as he had done, and stared out into the darkness of the night. Vaguely I could discern the black bank of the trees and the lighter expanse of the moor, for the moon was behind the clouds. And then I gave a cry of exultation, for a tiny pin-point of yellow light had suddenly transfixed the dark veil, and glowed steadily in the centre of the black square framed by the window.