Spirit Combat

Spirit combat is an opposed POW roll, with the ghost initiating the attack. If an investigator fails to win the opposed POW roll, they suffer the loss of 2D10 to 3D10 POW (powerful ghosts inflict greater damage)—in some cases, this naturally regenerates at 1D10 points per day after 24 hours, although some ghosts can inflict permanent POW loss (the Keeper should determine if loss is temporary or permanent). If an investigator wins the opposed POW roll, the ghost loses 2D10 POW.
Some investigators (such as heroes from Pulp Cthulhu) may be able to initiate spirit combat; if so, make the same opposed roll, with both investigator and spirit taking turns each round to initiate and then defend against an attack, just as in normal combat.
See Goody Fowler's ghost