Stars – Dead Hearts lyrics

I believe its a metaphor about the loss of innocence and love. A girl sheltered from the world ventures out into it and finds that so many people out there have no genuine innocence left inside, presumably because of times they were hurt emotionally or physically. She realizes that they are all dead hearts with no passion or love or innocence left inside. She is so hypnotized by these awful new creatures and her friend/lover is taken with them also, and questions her as to how they got that way.

I believe it is a conversation between a young girl and someone close to her after a near death experience. You can almost tell when she says "They had lights inside their eyes... They had lights inside their eyes..." This refers to them being angelic or at least radiant. When she died that's why she didn't see what the other person is asking, she was gone. Though of course "The closing window and the slamming door" could be a reference to heaven and hell, hell being the slamming door and heaven being the closing window.
There is more in the first verse that proves it is a conversation between a young girl and someone else after she almost dies but comes back, like when she says "They moved forward and my heart died" She's talking about the people that were coming for her the "kids that I once knew." Which is people she met in life. Her heart dying is really only a metaphor for like the sinking feeling you occasionally get in your stomach. She felt this because she knew she had so much to come back to and wasn't ready to leave. I mean she obviously had someone that cared enough for her to talk to her after she came back. In the second verse when the questioner is asking "Did they seem too real to you?" He wants to know just how far gone she was. The whole verse is basically the questioner wondering how far gone she was is and the young girl replying with things like "They make me feel I'm falling down..." Which is the girls way of saying they made me just unbearably sad. In her case it's okay she just came back, she just saw the representation of people that she once knew. "They were kids that I once knew..." this line doesn't actually refer to children that have died but to what she see after she dies which is a representation of the kids that she once knew. Knew is in a past tense because she is still getting over the fact that something traumatic happened to her and she died but she came back. Dead hearts are people like her people that have been through a near death experience.

I know it may not be the official meaning of the song, but I always associate it with the Holocaust. A girl comes back from the concentration camps alone and meets up with an old friend. He asks her how it was there, only she is too hurt to talk about it, so she answers a little weird. She didn't really know the people there and still felt a connection. But they're all gone.