Have you ever known someone who just disappeared? I was talking to someone today whose father recently died. He has been trying to contact his dad's brother, who vanished about 30 years ago, leaving no trace. They've put appeals out on social media, but no luck. The journalist AA Gill's brother also disappeared like this and was never seen again.
It made me think of a neighbor I had years ago. When I first moved in with my ex, I got to know a woman who lived opposite. Her husband was ten years older than her and a bit of a bully/control freak. We saw each other almost every day for years and became quite close, then she vanished. She'd told me that she was saving money and planned to leave him one day, but it still came as a shock. I never saw or heard of her again.