In Ithaca, New York, in 1929 , John Alden tells a gathering of academics that he is a visitor from the twenty first century-that he washed up on their campus after tumbling over a waterfall in the year 2010. He further claims to be a retired New York City detective who went over Ithaca Falls in pursuit of a serial killer. The revelation sets off weeks of trepidation in the storied hills of Cornell University as the strange visitor tells of an attempt to alter the course of history by assassinating Franklin Roosevelt.