VAULT OF EVIL (1973) #5

Reprint of the 6th story from Spellbound #12 A doctor and his friend cook up a plot to acquire the family fortune by the doctor declaring the man dead and then he pretends to return as a ghost and scare the remaining members to death. But the doctor wants all the money and betrays the man by injecting poison into him rather than a drug to make him appear dead, and so he realizes at the end of the story that he actually is a ghost. He kills the doctor.