Serial killer. Hook hand. Back seat.

Suggested by SolamenteDave

As an aside: When I was taking drivers’ training, our instructor was absolutely insistent that we begin every drive by walking around the car to inspect our tires, peer in the backseat, and check underneath in case there are any unwanted intruders. One week, I thought I was real smart: As I checked the tires, I found that my instructor had placed the keys behind one. In my triumph, I neglected to check the backseat, where he had planted someone to grab me as soon as I sat down. It’s a lesson I never forgot.