Two strangers knock on the door of Dr. Samuel Mudd (Dennis Weaver). One has a broken leg. Mudd fixes it, and becomes an unwitting conspirator in the murder of Abraham Lincoln when his patient turns out to be a fleeing John Wilkes Booth. Railroaded by Lincoln's secretary of war (Richard Dysart), Mudd is found guilty and sentenced to life in Fort Jefferson Prison. His wife, Frances (Susan Sullivan), however, won't rest until her husband's wrongful conviction is overturned.