I thought it was about a girl he loved who was dieing as well, but i went to one of their shows and alex said:
"This is a song for any of those who has ever been cheated on." so if you listen to it again it knowing that he was being cheated on, it makes a more sense. He probably went to her house to find out why she had been avoiding him and when he got there probably saw her in bed with another guy (when i caught her in bed she looked much happier then) and now he knows thats why.
I thought it was about a girl he loved who was dieing as well, but i went to one of their shows and alex said: "This is a song for any of those who has ever been cheated on." so if you listen to it again it knowing that he was being cheated on, it makes a more sense. He probably went to her house to find out why she had been avoiding him and when he got there probably saw her in bed with another guy (when i caught her in bed she looked much happier then) and now he knows thats why.