It’s an episode of “The Voice”… with Ghosts.
So, sure… you’re an ambitious up and coming opera singer. You want to get ahead. So you’ll take advice wherever you can get it. Even if it comes from behind the wall of your dressing room. Your floor length mirror also opens up to the catacombs, and… never mind.
This will all make total sense when you listen to “Let Me Love You Now”. This beautifully seductive song would make me walk through a mirror any day.