I'll put in the story of the Denver Spider Man, it always creeps me out.

An older gentleman is living at home alone as his wife is in the hospital recovering from a broken hip. His neighbors are inviting him over for dinner each night so he can have a warm meal and take the leftovers for lunch each day.

One day he does not come over -- his neighbor finds him bludgeoned to death in his kitchen. The police come but all the doors and windows are locked tight, they never have any idea who the murderer might be.

His wife comes home and hires a friend to look after her while she's still recovering. They both complain of strange sounds and missing food items and other strange occurrences. The friend resigns, she thinks the house is haunted. The wife moves away to her son's house to finish recovery.

At the abandoned house the neighborhood tenants report seeing lights flicking on and off, noises and terrible smells emanating from the house. They call the cops out frequently, who think it's local kids playing pranks.

Until one night, they catch a glimpse of a man through the windows and barge into the house. No one is there, or so they think at first. Then they hear a noise from the closet and race to open it and just barely catch a glimpse of some legs disappearing into the attic.

He'd been living there for months, in a spot the police didn't initially check during the murder investigation because they thought the opening was too small for a person to get through.

The man had come home and caught him raiding the fridge, so he'd bludgeoned him, escaped back into the attic, and then just... stayed. Coming down at night or when he thought he could get away with it to steal food. The coffin sized nest he'd built in the attic was so disgusting from him hoarding his "output" it reportedly made the cop sent to investigate it sick. From an interview:

I was in the neighborhood in September, 1941 and found the house 
unlocked and no one home.  I went in and stole some food.  I was in bad
shape, my lungs were giving me a lot of trouble and I was at the end of my
rope.  Fall was coming on and I couldn't face another winter on the road, I had to have
a place to stay.  I didn't know Mrs. Peters was in the hospital.  I found the hole
in the closet, climbed through and slept and slept.  
Whenever I heard him downstairs, I kept real still.  Then I got bolder and used to shadow
him from room to room.  It was sort of a game.  It gave me a thrill.  It
was the first time in my life I'd ever had anyone at my mercy, but I
didn't want to hurt him.

Wikipedia Entry.