After dinner, Holden convinces his friend Mal Brossard to let Ackley come see a movie with them. But when they realize that Mal and Ackley have already seen the movie, they eat hamburgers and play pinball instead.
While Stradlater's on a date, Holden wanders around with boys. At the same time, Holden acts compassionately toward Ackley.
Back at Pencey, Ackley hangs out in Holden's room telling a story about having sex with a girl, which Holden knows is a lie.
Ackley seems to have similar teenage issues about sex as Holden.
Holden finally gets Ackley to leave by starting Stradlater's composition. Though it's off topic, he writes about his brother Allie's baseball mitt, which Allie had covered with poems. Holden was thirteen when Allie died of leukemia at age eleven on July 18, 1946. He describes Allie as kind, innocent, and the smartest person in his family. The night Allie died Holden slept in the garage and broke the windows with his bare hands.
With the revelation of Allie's death, suddenly Holden's teenage insecurity and alienation doesn't seem quite so typical. Allie's death in childhood certainly makes it seem like life's "rules" are arbitrary and cruel, and provides an explanation for Holden's fixation on childhood. Punching window panes is a sign of severe unhappiness.