[MargaretR]

I know this sounds weird and I will probably get some flack for posting it, but I am only trying to help.

On a 'paranormal' forum I found a thread which related supernatural pranks using alarm clocks. I suggest you place some natural rock salt next to that clock. (worth a try?)

I had a night time doorknocker, which roused me in the small hours, only to find the stairwell empty and the exterior doors were locked. I placed some chunks of himalayan rock salt on my landing table next to the door, and the knockings have stopped.