Mary Winchester haunts the Winchester family home years after her death. Her spirit manifests initially as a fiery entity visually echoing her fatal demise before revealing her identity. When a poltergeist attacks her sons Sam and Dean during their supernatural investigation, her ghost intervenes. She frees Sam from the entity's grip and confronts it directly, demanding it leave her home and release her son. After protecting them, she communicates briefly with Sam and Dean, expressing pride in Dean. She then sacrifices her spiritual presence to permanently banish the poltergeist from the house.

Within a djinn-created altered reality, Mary Winchester exists alive and well, unaware of the fire that originally killed her. This version, portrayed as a widow following John Winchester's death a year prior, experiences an ordinary life. She celebrates a birthday with her adult sons Dean and Sam, along with Sam's fiancée Jessica. Mary interacts warmly with Jessica and appears content within this family setting, though the reality is ultimately exposed as an illusion designed to ensnare Dean.

Her ghost's ultimate fate after expelling the poltergeist remains unspecified.