What is the “rather harrowing scene that Gatsby has outlined in the garden” that Nick refers to in the 18th paragraph of Chapter 7 of The Great Gatsby?
In Chapter 6, Nick acts as a lookout and “remained watchfully in the garden” as Daisy explained “in case there’s a fire or a flood… or any act of God” while Gatsby and Daisy “sat on the steps [of Nick’s house] for half an hour.
Gatsby’s garden is mentioned again right before they leave the Plaza Hotel in Chapter 7. Nick is “startled at [Gatsby’s] expression. He looked—and this is said in all contempt for the babbled slander of his garden—as if he had ‘killed a man.’ For a moment the set of his face could be described in just that fantastic way.”
Having planned and dreamed of his being reunited to Daisy after five years, Jay Gatsby is in a fanatical, emotional state in Chapter Seven. Prior to this, in Chapter Six, he has spoken with Nick, who relates that Gatsby
wanted nothing less of Daisy that that she should go to Tom and say: 'I never loved you.'
Further, he informs Nick that he is going to "fix everything just the way it was before," recapturing the past and his youthful idealism and "the incomparable milk of wonder," as Nick phrases it. Now, in Chapter Seven, Gatsby invites Nick to lunch for this "rather harrowing scene" of confronting Tom with his and Daisy's love. Before this confrontation, however, Tom sees Daisy kiss Gatsby and tell him she loves him.
Later, when Nick and the others drive to New York City and the Plaza Hotel, there is a very tense confrontation in the rented room as Gatsby informs Tom that his wife does not love him. An incredulous and insulted Tom retaliates with information he has uncovered about Gatsby's dealings. With the tension created between the two men, Daisy stares "terrified" between Gatsby and her husband. When Nick looks back at Gatsby, his facial expression is that of a man who has "killed a man."
Nick adds that although he has never believed any of the gossip of Gatsby's guests in the garden during his lavish parties that he has killed a man, Gatsby has this murderous look. Interestingly, earlier in the chapter, he has also described Wilson as so sick that he looks "guilty." Here, again with Gatsby, Nick draws the comparison of sickness of the heart with guilt. This "rather harrowing scene" of having his dark and clandestine criminal activities exposed before Daisy during his confrontation with Tom Buchanan over the love of Tom's wife threatens Gatsby's dream of recapturing his idealized past, and he is, thus, angered and sickened both, as though he has "killed a man"--that man being the youthful and idealistic Jay Gatsby.