In December, 1860 Theodora Kydd arrives by stagecoach at Shawneetown on the Ohio River in southern Illinois. She is a retired nurse who has been sent by Chicago's Allan Pinkerton to investigate unusual sightings of a sometimes island that can be seen from Shawneeetown's shore. Mrs. Kydd husband, Dr. Kydd, was a victim in the Lady Elgin steamer disaster on Lake Michigan between Chicago and Milwaukee; this fact comes into play at novella's end. Theodora Kydd interviews local residents about the elusive island. Old "Blue" Leech, a Revolutionary War veteran and Yale University graduate, says if Mrs. Kydd could interview Robert Ingersoll, a past resident lawyer, along with Abraham Lincoln who used to include Shawneetown in his circuit riding, they could provide her with further insights into the apparition. When Mrs. Kydd takes a buggy ride out to the local cemetery, she finds old Blue's body in his above ground tomb where, by the looks of things, he has been interred for some time. Mrs. Kydd goes to an island enveloped in fog where she speaks with an Indian who complicates her mission. Returning to Shawneetown, Mrs. Kydd finds that it has been devastated by a flood.