Nick, played quite well by Joseph Gordon-Levitt, starts masturbating when he's eight and his baseball coach starts having sex with him a year or so later. Nick starts making money on the streets in his little town and nothing really bad happens until he moves to New York where there are not only more knowledgeable men, but more men interested in kinky sex, including pain. His mom sends him a ticket home for Christmas.
At the same time, Bryan thinks he was abducted by aliens when he was eight and also played on the baseball team. He continues to watch TV shows and think he sees aliens, and then meets a teenage girl who was on TV. She keeps making him come to see her and eventually she comes to his house and tries to kiss him. He kicks her out.
At this point, Bryan has figured out that something about the baseball team is what has made his nose bleed, and he finds Nick. They break into the home of the baseball coach and Nick carefully tells Bryan what the coach did to him to cause the bleeding and so forth.
That's the end of the movie, but near the beginning, after Nick has been raped by the coach, Nick himself rapes Bryan (on Halloween) and Bryan's nose bleeds. I kept wondering if Nick was actully the cause, not the coach, and since Bryan was so gullible, Nick was able to make him think the coach was responsible.