| I think I know... Izzy-Denny
If I may, I think I have a clue. perhaps the answer !!!!!!
Think of the movie Sixth Sense. It was so cleverly written and presented, but I think this is how it will play out....
I think Izzy was pushed over the edge after Han found out she stole the heart for Denny, that she committed suicide, or had and accident. I think she is dead !!!!!! Denny kept saying, "I am here for you Izzy".. He may have actually been saying, "I am here for you" as in to bring her over to the other side, go to the light , so to speak. And, perhaps Alex was being haunted by Izzy as he was speaking to her and he burnt the sweater. Only after the sweater burned, could Izzy touch Denny.
I may be way off, but I am so psyched. | 
