The séances at which the figure appeared followed a form that was standard in the materialisation mediumship of the 1870s. The medium, Florence Cook, was placed in a curtained recess or an adjoining room, sometimes bound, sometimes sealed in with tape and thread, and the sitters waited in near darkness in the room outside. After an interval a figure in white drapery came out through the curtain, walked among the sitters, spoke, allowed itself to be touched, and withdrew.
William Crookes, a chemist of established reputation who had already published on the physical phenomena of mediumship, took the case up in 1873 and 1874 and held sittings in his own house in London. He photographed the figure by artificial light on a number of plates. He published his account in the spiritualist press, stating that he had compared the figure with the medium on points including height, complexion, ear piercing and pulse rate, and that the differences convinced him they were two persons; on one occasion he reported seeing figure and medium at the same time.
The conditions that made his testimony possible are also what has always undermined it. The light was low, the photographs show a draped figure whose face is often obscured, and the arrangements gave him private access to the figure inside the cabinet in a way no controlled protocol would allow.
The atlas records Katie King as a figure that was claimed and photographed under those conditions, not as a person who lived, and the entry that follows sets out why the case has never been closed.