This song is about Gerard's dead grandmother. Her name was Elena but her friends called her Helen, so he thought of her as Helena. She was also a dancer which is why in the music video the girl in the coffin comes up to dance. And also why he says "Are you near me? Can you hear me?" It was also said that when they started the music video filming it was too much for Gerard and he got really emotional.
Newayz, I just love this song.