On May 2, 1519 at the Clos Luce in Amboise, Leonardo is dying. He no longer cares about art or science. He wants only to answer a simple question about his life: why did he abandon his colossal equestrian statue in Milan?

Meanwhile, R-, a 20th century historian writing a novel about Leonardo, meditates upon the same question in the midst of an apocalyptic traffic jam, as military helicopters fill the air with tear gas, AIDS demonstrators run amok, and a hospital evacuates its patients onto a nearby sidewalk.