On July 17, 1981, a huge crowd of Friday night revelers had gathered inside the elegant Hyatt Regency hotel in Kansas City, Missouri. Like a number of other newly built Hyatt hotels, this one had a dramatic interior atrium that enclosed four stories under a steel and glass roof. With its adjoining restaurants and bars, the atrium space had become one of the city's most popular entertainment venues. By seven o'clock, an estimated sixteen hundred people had shown up for the night's tea dance with live music.

Scores of the partygoers were watching the throng of dancers on the lobby floor from a second-story skywalk, in effect a hanging sidewalk along the west side of the atrium that connected two wings of the building. Even more couples were on the fourth-floor skywalk directly above (the third-floor skywalk was offset from the other two). A bar was set up...