3rd Sunday of Easter

When Jesus appears today to His disciples and says, “Peace be with you,” they at first think it might be a ghost.  Ghosts and the supernatural are not talked about very much in our current Church culture.  What do we believe as Catholics about ghosts?  What if we or someone we know claims to have experienced a presence beyond this physical world?  Should we be afraid?  Can they hurt us?  Or can we help them?