April 27, 1891: Holmes learned Moriarty had escaped. [FINA]
On the Monday morning Holmes had telegraphed to the London police, and in the evening we found a reply waiting for us at our hotel. Holmes tore it open, and then with a bitter curse hurled it into the grate.
“I might have known it,” he groaned. “He has escaped!”
“Moriarty?”
“They have secured the whole gang with the exception of him. He has given them the slip. Of course, when I had left the country there was no one to cope with him. But I did think that I had put the game in their hands.[…]”
Date provided by the volume A Day-by-Day Chronology of Mr. Sherlock Holmes, according to Zeisler and Christ, compiled and edited by William S Dorn.