In the spring of 1893 tough Chicago detective Mike McGhan and his partner Henry Bockleman are beset with problems arising from the World’s Fair. The millions of visitors coming to Chicago have overwhelmed the detective bureau. Why are so many people disappearing? All other missing persons cases are put on hold when a plot is uncovered to kidnap the inventor whose alternating current lighted the fair; Nikola Tesla.
To add to Mike’s woes, his girlfriend Mary Cassidy, who is half Lakota Sioux, accepts a lucrative offer to ride in Buffalo Bill’s Wild West show which is set up right outside the fairgrounds. When they have a falling out over her dangerous new job, Mary begins seeing a charming but sinister doctor who owns a nearby hotel.