The Six Napoleons
'Now you can see how the matter begins to get clearer. The other fellow is probably also an Italian, and also a member of the Mafia who has broken the rules in some fashion. Pietro is set to go after him. Probably the photograph we found in his pocket is the man he was following, so that he would not knife the wrong person. So he followed the fellow, he saw him enter a house, he waited outside for him. Then there was a scuffle and he himself was killed instead of the person he meant to kill. How is that, Mr. Sherlock Holmes?'