In "The Open Window" by Saki, when does Mr. Framton Nuttel run out of the Sappleton's house?

In Saki's "The Open Window," Vera, a young girl of fifteen, takes advantage of a weak man's ignorance to play a practical joke on him. She sets up the scene perfectly by first asking if he knows anyone in the area. When Mr. Nuttel says that he does not know anyone, the girl tells him a tragic tale about losing her uncle and cousins to a hunting incident a few years earlier. Vera must be a great storyteller because her tale is believable and probable by the way she describes it. Additionally, Vera's timing and acting skills are perfectly executed because when the men come back from hunting, she pretends that she sees them as ghosts. Her response to the men, along with her believable story, convinces Mr. Nuttel that the young girl has been telling the truth, only to discover an unexpected ending. However, the point at which Mr. Nuttel runs out of the Sappleton's house is when one of the men starts to sing a song that Vera refers to in the story. The text reads as follows:

"Noiselessly they neared the house, and then a hoarse young voice chanted out of the dusk: 'I said, Bertie, why do you bound?'"

When Mr. Nuttel hears the man singing the song from the girl's story, he concludes that these are the three men from the story he has just heard. It is at this point that he grabs for his personal items and bolts out of the house and down the road. Mr. Nuttel not only proves that he is gullible, but that he is superstitious and probably believes everything he hears.