"The Dark Gathering - Episode 23" begins with Yayoi and Eiko returning home, where they see a news report about Ai and his divine spirit. This prompts Yayoi to call Keitaro to discuss the incident in Shiga Prefecture involving Ai's god and the spirit of death. Despite Keitaro's concerns, Yayoi decides to pursue the matter further, leading to an encounter with Dorothy, who shares Yayoi's ability to see spirits.

The plot intensifies when Dorothy suggests exploring the school's haunted spots, revealing her own ability to see spirits in the process. A flashback shows Dorothy at the Old I Watergate speaking with Oswald, hinting that she is controlled by a spirit who recognizes Yayoi's involvement in capturing another spirit.

The narrative then shifts to Yayoi's school life, where she investigates the authenticity of the school's ghost stories. Her inquiries catch the attention of her classmates Yoko, Futaba, and Aki, as well as Daisuke, who is skeptical of her beliefs. Dorothy intervenes and proposes a ghost hunt to test Yayoi's claims. Everyone agrees to participate after school.

During the ghost hunt, the group encounters a male spirit in Hanako's room and later a locked room where multiple spirits gather. Dorothy reveals her manipulation of the spirits and her experiment to observe their interaction with a vengeful spirit in the locked room. This leads to a climax as the group passes out in a mysterious mist after opening the door.

The tension rises as Yayoi learns about the horrifying past of the teacher's spirit, while the others face their own challenges. The violent actions of the teacher's spirit in the ghost world and its effects on Daisuke in reality add to the horror. Yayoi's struggle against the teacher's spirit is further complicated by the appearance of another spirit.

The episode ends with Dorothy on the school rooftop, watching the chaos unfold.