Emotionless?

A boy of merely 14 years old, Derek, has to take his mother out of an abusive home to somewhere he believes is a better place. He was right. Now he is 18 and a legal adult. One night someone he doesn't know comes to his front door. A very broad but seemingly starved man comes to his apartment asking for some help. Being the kind of person Derek is, he lets him in. Now the seemingly emotionless Derek who doesn't talk to anyone but his mother is entrigued by this boy. Why?