Walking shadows.

People across the globe have reported seeing these black, two-dimensional, human shapes stalk the bedrooms and hallways of their homes. Sometimes these Shadow People ignore you, sometimes they pay all too much attention, but they are always sinister.

Although there are many theories as to what they are - ghosts, demons, aliens - there is one thing for certain regarding these walking shadows. They're a mystery.

"I've seen them three times," an anonymous poster to 'From The Shadows' wrote. "Two times in the daytime with my sister, and once by myself at night. What really is it?"

No one knows for certain, but the people who encounter them know they exist.

"There truly are a such thing as these Shadow People," 'Shadows' reader Mike H. said. "I have had my own encounters."

The first was when something wrenched Mike from sleep.

"This one started off waking me up in my sleep by smacking me," he said. "Then I felt uncomfortable and started sleeping with lights, TV and door opened a crack."

But the door started slamming shut, but only when Mike slept.

"This happened several times, and, no, it was not wind and it was not another person. Believe me, I checked," Mike said. "That is what my first conclusion was, until it happened."

The door slam jolted him from sleep. He sat up and looked at the door. He wasn't ready for what he saw.

"I initially looked up at the door and what I seen shocked me," he said. "There was a tall Shadow Man standing above me at the door and it had both its hands up as if in the motion like it just got done slamming my door."

There was no confusion as to what had slammed his door, because Mike had left his bedroom light on. The Shadow Man was in full view.

"Before I seen this Shadow figure, I kept telling myself that, 'oh it's just a muscle spasm, nothing smacked me,' or, 'oh, it must be neighbors messing around or wind blowing against the door and causing it to slam like that.' But when I seen this thing, there was no denying it anymore, I had either a ghost or evil entity in my room."

Then it was gone. But not forever. The Shadow Man still haunts Mike's room, often enough Mike gave it a name, Casper the Unfriendly Ghost."

"I think it is something more along the lines of an evil entity or maybe a demon or some other form of being and not human," he said.

Carl has seen the Shadow Man, too, and, much like Mike's sighting, the room was well lit.

"Back when I was about seven years old, I was walking to the kitchen to go eat breakfast," he said. "On my way there, I ran into a black cloud hovering above the floor but didn't pay it much attention and walked right through it, at which point it vanished."

But the black cloud in the kitchen hadn't really gone.

"About 10 minutes later, while I was still in the kitchen, I saw a completely black figure with blood-red eyes watching me through the window," Carl said. "As soon as it saw that I had noticed it, it ran through the wall (out to) my front yard. Strangely, my parents were looking in the same direction and did not see anything."

Carl thought the red-eyed Shadow Man had left him that day, but he was wrong.

"More recently, I have begun noticing figures similar to the one I saw eight years ago walking around," he said. "No one but myself seem to notice them, and they do not run away or disappear when seen, they just stick to dark secluded and hidden corners, watching as though some untold event is about to transpire."

Another anonymous "Shadows" poster saw the Shadow Man in March.

"Four nights ago I was sitting on my bed, laptop on my lap, and something suddenly caught my attention," the poster said. "At the foot of the wall a shadow started to grow and crawl up the wall."

Anonymous slowly reached over, picked up his cell phone and snapped a picture of the Shadow.

"As soon as I snapped the picture it stopped moving up the wall, paused for a second and then faded away," Anonymous said. "The whole thing did not last more than six or seven seconds. I didn't feel anything negative or evil from the Shadow. If anything it felt like I had surprised it and once it noticed I was watching it, it got out of there."

Trying to avoid ridicule, Anonymous closely guards the photo and his identity.

"I have only shared this with a few trustworthy friends as it has been my experience that most people laugh, make fun of such things, call a person names, and mock them," Anonymous said. "Because of people like that we may never find out what these things are. No one wants to be thought of as crazy, delusional, or a liar, so they won't seriously investigate it. The ones that do try to find out what things are are not taken seriously by the scientific community.

"Anyways, that is my story."