In the novel Rumble Fish by S.E. Hinton, Steve and Rusty James have not seen each other in five or six years. Rusty James tells Steve that he was at the reformatory for five years. One of the things he mentions is that he was put into solitary confinement once. This is significant because Rusty James is afraid of being alone: he tends to break out into a sweat and to become nervous on such occasions. When Rusty was two years old, his mother left the family, taking along Rusty's older brother, Motorcycle Boy. When their father found out what she had done, he went on a three day drinking spree. Rusty was left alone for all of those three days and has never been the same since.
When Steve asks him how long he was at the reformatory, Rusty James doesn't want to remember; talking about the reformatory brings back memories of how he got there. It also reminds him that the brother he has idolized for most of his life is dead, shot by police officers while he was trying to release some stolen Japanese fighting fish into the river.
In the conversation, Rusty reminds Steve that the long scar on the side of his body was the result of a knife fight. Steve tells him that he remembers because he was there; he tries not to look for the other scars on Rusty's body. This is significant because Rusty was known for picking fights and picking up girls before he left for the reformatory.
When Steve jokingly asks if it would be safe to introduce his girlfriend to Rusty ("...you leave other guys' chicks alone?"), Rusty assures him that he has his own girlfriend. The two eventually decide on a time and a place for dinner, but Rusty realizes that seeing Steve again isn't really a happy occasion after all. This is because Steve's desire to remember the good old days just brings back uncomfortable memories for Rusty and the knowledge that, with his brother's death, 'he'd be alone the rest of his life.'
So, the information that is revealed about Rusty from the conversation is:
1) Rusty still doesn't like being alone.
2) He has changed his views about having more than one girlfriend at a time.
"Yeah....I got a girl."
"Or two or three?"
"Just one... I like to keep things simple..."
3) He doesn't want to remember anything from his past because it is too painful.