Answer:
The part of the text that can be marked as the point of climax is:
While the evening deepens, Mr. Nuttel sees three men and a dog walking in through the same window.
Explanation:
In literature, climax is when tension reaches its peak in a story. After developing the conflict throughout the story, an author solves such conflict in a tense, dramatic moment - the climax. Then, the tension decreases and all there is left is to present the solution itself and conclude the story.
In Saki's "The Open Window", the conflict developed concerns the disappearance of the men and the dog, and the fact that the aunt waits for them to return every evening. The climax, the most dramatic moment of the story, happens when Mr. Nuttel sees them return, walking in through the same window. The reader, just like Mr. Nuttel, is most likely surprised by this unfolding of events.