Why does Beloved haunt the house at 124?

Although the novel does not provide a precise answer to this question, the most plausible reason Beloved haunts 124 is that this house is where her murderer—that is, her mother, Sethe—lives. Beloved is a ghost story, and ghosts conventionally haunt those with whom they have unfinished business. Thus, Beloved haunts the woman who was supposed to nurture and protect her, but who took her life instead.