In the story "The Interlopers," in addition to the unexpected appearance of the wolves is the surprise to the reader that he or she is surprised for the second time. That is, "the fierce shriek of the storm" causes an old tree to split and fall upon the two mortal enemies, Ulrich von Gradwitz and Georg Znaeym, pinning them under the huge branches. When there are trapped, each threatens the other with his men's arriving before the others. However, when von Gradwitz suddenly offers his flask to Znaeym, the reader is rather surprised that after their heated arguing, Ulrich von Gradwitz should be gracious enough to lend his flask and call Znaeym neighbor. However, faced with possible death, Znaeym considers peace, himself, and jokes,
How the whole region would stare and gabble if we rode into the market square together....And what peace there would be among the forester folk if we ended our feud tonight....
At this point, the conflict between the two old enemies seems resolved and the reader is prepared for the denouement in which one of the men's hunting parties appear. But, for a second time, the reader is taken aback by an unexpected turn of events and a new conflict introduced at the very end of the story! Thus, the ending is a "surprise ending" because it is completely unexpected and because it introduces at the conclusion of the story a second surprise as well as a conflict.
The ending to this story is a surprise because it's not what you would have expected to happen. All through the story, there has been a conflict, right? The conflict has been between the two men. So you would expect that the ending would have something to do with their conflict.
The first time I read the story, I thought they had made up and would be friends. If not, I figured the one guy whose men were coming would kill the other after pretending to make up.
But wolves? Where did they come from? We never had any idea it would be wolves, or at least I didn't. So it's surprise because we get these wolves that had not even really been mentioned and they end the story.