Ancient round of existences (Sanskrit, samsara) we cycle through endlessly due to ignorance and craving, the Wheel of Rebirth and Death (Hanciong/Flickr). Stories of the Departed
Spooks, creeps, haints, poltergeists, monsters, ghosts... in Buddhism? The Petavatthu is a collection of ancient Buddhist scriptures in the form of ghost stories. It is located in the Khuddaka Nikaya. Composed of 51 verse narratives, it specifically describes how the effects of unprofitable karma can, when and if they ripen, lead to rebirth in the unhappy realm of "ghosts" (petas).This happens in accordance within the framework of intentional actions and their results. It gives prominence to the teaching that giving alms to successful Buddhist practitioners (arhats, buddhas, meditators, monastics, moral individuals) is capable of benefiting the ghosts of one's relatives.
But how could my good actions become someone else's good actions? They can not, technically speaking. But since "actions" include words and thoughts, there is a way. If one's relatives in the realm of ghosts approves, lauds, and commends the good one does either on their behalf or in general, they themselves are generating very meritorious mental-karma.
When the deed they are approving of is very excellent, such as giving to an enlightened person, it can have immediate benefits for them. That a relative does it is important, that they approve of it is crucial. The other worlds are not far.
Hungry Ghost (Sanskrit, preta) scroll, Kyoto (Wikimedia commons)