Having finally introduced his entire ensemble cast, Hemingway begins here to use it to its fullest effect, like a chess master moving pieces around a board. Brett rejects Cohn outright. Having been trusted by his mentor Montoya to look out for Romero, Jake betrays the former by first introducing the young matador to his decadent friends, and then actually fixing him up with the plainly-destructive Brett. Brett has hurt Mike, Cohn, and Jake himself; it's hard to imagine that she won't harm the younger and far more naïve Romero. Meanwhile, Mike cannot get past the fact that his fiancée slept with Cohn, and tensions between the two men mount.
As late in the story as we are at this point, characterization nevertheless continues. Jake tells Brett that he'd behave just as badly as Cohn, if given the opportunity, to which Brett replies, "Darling, don't let's talk a lot of rot." Again, Cohn's primary function in this book is to serve as Jake's foil — to make him look good, really. His behavior in this chapter certainly accomplishes that.
