(The following text is adapted from "Watseka Wonder" (1879) by Dr. E. W. Stevens, the Spiritualist doctor who witnessed the supposed possession of Lurancy Vennum by Mary Roff and then wrote extensively about it.)
The year is 1865. The town is Watseka. A young woman, Mary Roff, dies a mysterious death after a lifetime of fits and seizures that robbed her of her youth, her personality, and her soul. Many thought she was mentally ill. However, some thought her illness was something other than natural.
In the years following her death, her family — the Roff family — came to be convinced of the latter. They became Spiritualists, and they believed that the spirits of the dead were alive, and that under given circumstances they could bring messages to the living and even temporarily inhabit another body, dwelling for a time in an earthly home.
In 1877, twelve years after the death of Mary Roff, in the same town another girl, Lurancy Vennum, began showing symptoms very similar to those of the deceased Mary. She begins having fits and seizures. She talks in strange languages and garbled speech. She claims to see people around her and takes on different personalities, as if possessed by the spirit of another.
Watseka is in an uproar. Townspeople believe her to be insane—just like the Roff girl—and they want Lurancy committed. However, the Roff family, now Spiritualists, suspect that some other illness afflicts the Vennum girl, just as it had their poor Mary.
Asa B. Roff, Mary's father, asks to meet with Lurancy, and he brings along Dr. E. W. Stevens, a Spiritualist doctor. They see her in the throes of her spells. And after being possessed by the strange spirit of Katrina Hogan, a kindred spirit asks to take control of Lurancy's body: it is the spirit of Mary Roff.
Mary explains that the Vennum girl is very sick and must return to heaven to be curerd by the angels. In the meantime, Mary asks to go home with her family, and with the permission of Lurancy's reluctant parents, she moves into the Roff Home for three months and ten days, from February 10 to May 21, 1878. The Roff Home is where Lurancy stayed and where the stories described in the account by the Spiritualist doctor E. W. Stevens, who treated Lurancy while she was afflicted.