What's the most disturbing secret you know about someone that would ruin their life if exposed—but you stay silent, pretending you don’t know?

My friend cheated on her boyfriend early in their relationship. Now their families think they’re a match made in heaven, planning an engagement soon. But here’s the thing—only I know the truth. She’s done this before, like it’s a habit she can’t break. Watching them smile, pose for photos, make future plans…it’s like witnessing a beautiful lie wrapped in wedding prep. And I’m the only one holding the secret that could burn it all down.