On April 14, 1961, young professor Peter Corrigan is involved in a discussion with colleagues at the Potomac Club on the question of whether events in history could be changed if time travel were possible. After bumping into an attendant named William on the way out, Peter feels faint. Confused by the gas lamps and horse-drawn carriages on the street, he notices that he's wearing clothes of a much older style and decides to walk home. He finds that his "home" is a boarding house, and in discussion with the strangers he meets there, he discovers that it's April 14, 1865, the day of Abraham Lincoln's assassination.