Does the Bible speak of ghosts as being real? (Halloween)

There are a few references of people in the Bible thinking they were seeing a ghost.  One such reference was when Jesus was walking on the water to the disciples (Matthew 14:26).  Another was when Jesus made an appearance to the disciples after He resurrected (Luke 24:37).  However, the Bible is clear that there is no such thing as ghosts (people who have died but their soul is still on the earth).  Most of the time people who think they have had encounters with ghosts are just letting their imagination run wild.  Other times it may be demonic activity.  Either way, when a person dies their soul goes to Heaven or Hell depending on whether they believe in Jesus or not.