Sophie had a strange feeling that something wasn’t right in her house. Every night, she would wake up to the sound of her phone buzzing, only to find dozens of photos in her gallery—photos of her, sleeping. She lived alone. Panicked, she deleted them, thinking it was a glitch. But the next night, more photos appeared. This time, the photos were closer, as if whoever was taking them was right next to her bed. She set up a camera to catch whoever it was. The following morning, she checked the...