“Please… let me out. I’m afraid of the dark.”

The trembling whisper pierced the early morning silence in a mansion on the outskirts of San Diego. Daniel Harrington had just returned home unannounced after abruptly canceling a business trip to Berlin. For three nights in a row, he’d had the same nightmare: his young daughter crying, calling for him from somewhere enclosed. This time, he decided not to ignore the feeling that gripped his chest.

It was exactly 2:00 a.m. when he went upstairs to his eight-year-old daughter Lily’s room. The door was ajar. As he gently pushed it open, Daniel felt an eerie chill. The room was spotless. The bed was perfectly made, as if no one had slept there. Lily’s favorite stuffed animal was carefully placed on the pillow.

Then he heard it.

A soft, almost imperceptible tapping was coming from the built-in closet. Daniel caught his breath and opened the door.