“It is my business to follow the details of Continental crime. Who could possibly have read what happened at Prague and have any doubts as to the man’s guilt! It was a purely technical legal point and the suspicious death of a witness that saved him! I am as sure that he killed his wife when the so-called ‘accident’ happened in the Splugen Pass as if I had seen him do it. I knew, also, that he had come to England and had a presentiment that sooner or later he would find me some work to do. Well, what has Baron Gruner been up to? I presume it is not this old tragedy which has come up again?”

“No, it is more serious than that. To revenge crime is important, but to prevent it is more so. It is a terrible thing, Mr. Holmes, to see a dreadful event, an atrocious situation, preparing itself before your eyes, to clearly understand whither it will lead and yet to be utterly unable to avert it. Can a human being be placed in a more trying position?”

“Perhaps not.”