Elliot (or Eli as he is in the book), to me comes across as someone who has led a very sheltered life, and although he has moved away from his parents, he is still rather naive.
When he arrives at the Gramercy Warren, he is unsure what to expect, one thing he didn't expect was to meet someone he was attracted to, which he did find with Matthew. Although uneasy about being in the warren, he follows Matthew to his office, and then stays with him until late. When he goes to leave, he finds himself snowbound and staying in the warren - which actually scares Eli totally.
Eli is uneasy when seeing the Dead people and the vampires, but stays close to Matthew. He has no intention of staying long in the warren, just long enough for the storm to pass and the subways to re-open. However, this all changes when he meets Richard, and he does the unthinkable.
Now Eli has big decisions to make, on what he wants to do. Does he stay or does he go? Does he actually love Matthew or even Richard? Is there any kind of future for Eli in the Warren?