Well not sure if this would be considered a ghost.....but webster gives the definition of ghost as the following....
1 : the seat of life or intelligence : SOUL <give up the ghost>
2 : a disembodied soul; especially : the soul of a dead person believed to be an inhabitant of the unseen world or to appear to the living in bodily likeness
3 : SPIRIT, DEMON
With that in mind....
Saul needed counsel and got no answer from the lord....so he asked his servants to seek him a woman who could help him communicate with the dead and he went to that woman in order to speak with Samuel who was already dead at the time.(general gist of it)
From the book of Samuel
28:14 And he said unto her, What form [is] he of? And she said, An old man cometh up; and he [is] covered with a mantle. And Saul perceived that it [was] Samuel, and he stooped with [his] face to the ground, and bowed himself.
28:15 And Samuel said to Saul, Why hast thou disquieted me, to bring me up? And Saul answered, I am sore distressed; for the Philistines make war against me, and God is departed from me, and answereth me no more, neither by prophets, nor by dreams: therefore I have called thee, that thou mayest make known unto me what I shall do.