Holden goes to Mr. Antolini (his former English teacher) at 1:00 in the morning. Though Mr. Antolini has been out at a party with his wife, he invites Holden to come over when he calls. Mr. Antolini tries to counsel Holden about the importance of a good education.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of the mature man is that he wants to live humbly for one.
But Holden is tired and doesn't want to talk about it, so he lets his former student go to sleep on the couch. Holden wakes up in the middle of the night with Mr. Antolini stroking his head. Immediately, Holden assumes that Antolini is coming on to him, so he quickly gets dressed claiming that he has to go catch a train.
Whether or not Antolini is actually hitting on Holden is not explained. Instead, it seems that this is a caring male figure who is worried about Holden and his future. Instead of letting this man who was once a hero care about him, Holden pushes him away. Later at the train station, Holden begins to think he misjudged the situation, but it is too late.