The camera turns away from a character and then comes back, and something that wasn't there before is now in view. The audience keeps suspecting what's off-screen.
When a character looks around, when sweeping an empty hallway or yard, the "turn around and it's right there" moment.
Pan-away reveal, the camera holds on a man chatting calmly with a friend at a diner counter, then pans slowly left to the window, revealing a huge shadowy figure standing outside in the parking lot, 35mm lens, dim neon light, creeping dread mood, 6-second shot.
camera on a tripod slowly pans away from a woman in a quiet living room to an empty window, then pans back to her; a tall pale figure now stands behind her, she does not notice
It Follows (2014) — Critics singled out its carefully built 360° pan (Wikipedia). Each time the camera goes all the way around, a person who might be "it" is closer (Montages)