The narrator, a computer scientist, gets a letter from former colleague Bill Rigley indicating that he has discovered components of an analytical engine which was apparently built in rural New Zealand in the mid 19th century.
Traveling to New Zealand, the narrator is shown the machinery, which was discovered under a farm house near Dunedin as well as a book of scientific drawings and a journal.
While these beings lack the "outward aspect" of humans, they are clearly intelligent and have amazing machines, including powerful medicine.
Louisa takes sick and Luke determines to travel with her to the base of the "cold loving people" so that they may heal her.
The narrator and Bill use information provided in Luke's journal to calculate that the Heteromorphs' base was on South Georgia Island.