The Hound of the Baskervilles question

Watson was told by Barrymore, the butler, about a letter from L.L. which Sir Charles Baskerville received on the very day of his death. The letter was found in a fireplace and only several lines and the initials remained legible. This way Watson figured out that Laura Lyons was somehow involved. When he told Holmes about it, however, the detective already knew about the affair between her and Mr. Stapleton. It was suggested (though never explicitly stated) that Holmes, who was living on the moor and observing everything from the hiding, simply saw them meeting each other in secret.

On a burned envelope, there were the letters LL. Asking Mortimer, they found out about Laura Lyons. Then Holmes went to her office and showing the documents of his marriage with Ms. Stapleton, she told everything.

I can't recall either but I think it was the partially burned envelope with someone's initials on it; if I'm on the right case.

Didn't he see them in the garden arguing? Or was that Watson? I read a long time ago too.

I don't remember, sorry

Yeah, there's that too.

Yeah, there's that too.

Yeah, there's that too.

Yea that is what happened! Good one!

I'm on the same train with both of you, but I believe it was when he and Dr.Watson went to talk to her in her house, that was in a different town. Hope this helps :)