November 29, 1890: Culverton Smith confessed to killing his nephew, Victor Savage. [DYIN]
The very one, by George, and it may as well leave the room in my pocket. There goes your last shred of evidence. But you have the truth now, Holmes, and you can die with the knowledge that I killed you. You knew too much of the fate of Victor Savage, so I have sent you to share it. You are very near your end, Holmes. I will sit here and I will watch you die.
Source: A Day by Day Chronology of Mr. Sherlock Holmes according to Zeisler and Christ, compiled by William S Dorn, BSI, DWNP