You went to bed about an hour ago, when you suddenly wake to what you think is an intruder standing just out of sight to the left of your bed. Your heart is beating fast, it is hard to breathe, you are slightly confused, and as soon as you focus on the person, they're gone. Was it a ghost? Was someone really there? What the heck just happened? It was a ghost! Call Peter Venkman. You experienced a classle Nightmare, from the Old English for a demon sitting on your chest. This interpretation likely comes from the feeling of chest tightness associated with these events. You experienced a hypnopompic hallucination, connected to threat-assessment activity in your peripheral vision, likely controlled by activation in your superior colliculus. You experienced a Night Terror, and you likely fell back to sleep without prompting about a minute and a half later.