The ironic reversal for which the reader is unprepared in "The Interlopers" is the appearance of the wolves, an occurrence which neither Georg and Ulrich have anticipated. The reader expects one of the two parties of men to arrive and rescue at least one of the foes.
When the two foes are pinioned beneath the large branches of the old beech tree, each man threatens the other with the arrival of his men, who will help him but punish the other. Ulrich tells Georg,
“When my men come to release us, you will wish, perhaps, that you were in a better plight than caught poaching on a neighbor’s land, shame on you.”
And Georg threatens Ulrich,
When they drag me out from under these branches, it won’t need much clumsiness on their part to roll this mass of trunk right over on the top of you.
However, as the two enemies must remain trapped together, Ulrich begins to consider the peril in which they lie, and he decides to end their feud because it seems rather foolish to him now. After giving Ulrich's offer some thought, Georg agrees, and they share the warming wine from Ulrich's flask. Now,
...each prayed a private prayer that his men might be the first to arrive, so that he might be the first to show honorable attention to the enemy that had become a friend.
At this point, then, the reader anticipates the arrival of one of the rescue parties and the shock of these men when they find their master in such a perilous state. The reader is utterly surprised by this new amity of von Gradwitz and Znaeym, who have so quickly reconciled. It is with even greater surprise, then, to the reader that wolves comprise the surprise ending.