Is there such thing as ghosts?

Luke 16:19-31 kinda leads me to believe that once you're in Heaven we'll be pretty oblivious to the pain of this world and Hell. Which, in spite of Samuel visiting Saul in 1Sam28 (in direct violation of Leviticus 19:26) suggests that it's pretty unlikely that the souls of the departed really visit the living.

But I could be wrong- "There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy." ~Hamlet (who was visited by his father's ghost).

Still, I can't help suspecting that what people thing of as ghosts are often at best, their mind playing tricks on them or at worst, demons, dark-spirits, and Satanic angels posing as benevolent or benign spirits.

Beware of "meddling with powers you can't possibly comprehend" as Prof. Marcus Brody from the Indiana Jones films might say.