Professor Juan Manuel Barrientos prefers footsteps to footnotes. Fighting a hangover, he manages to keep his appointment to lead a group of students on a walking lecture among the historic buildings of downtown Mexico City. When the students fail to show up, however, he undertakes a solo tour that includes more cantinas than cathedrals. Unable to resist either alcohol itself or the introspection it inspires, Professor Barrientos muddles his personal past with his historic surroundings, setting up an inevitable conclusion in the very center of Mexico City.