Lee Harvey Oswald, Part II was the conclusion of a two-part episode Season 5 opening story arc of Quantum Leap exploring the JFK assassination, as Dr. Samuel Beckett leaps into the life of assassin Lee Harvey Oswald, at different points in his life leading up to the 1963 assassination in Dallas.
Also the 77th overall series episode, it was written by series creator Donald P. Bellisario, and directed by James Whitmore, Jr.. The episode originally aired on NBC-TV on September 22, 1992 with Lee Harvey Oswald, Part I as a two-hour episode.
Sam leaps into various points in the life of Lee Harvey Oswald (played by Willie Garson) in an effort to seemingly prevent him from killing President John F. Kennedy or find the truth about the events that day. However, the objective is made more complex by the fact that their minds are merging - Sam starts to believe he actually is Oswald.
If Al can't bring Sam back, it will be Sam Beckett who pulls the trigger on Kennedy that fateful day in Dallas. In the end, Oswald is the lone assassin of JFK (Al speculating that people made up the idea of a conspiracy rather than face the idea that we are all still so vulnerable that one man could kill the President that easily). Sam makes a final leap into U.S. Secret Service agent Clint Hill who climbed on the back of the President's limousine during the assassination.
In the final scene, Sam agonizes over the fact that he couldn't save the President's life, and accomplish his mission. Al says that maybe Sam did. When Sam responds that he didn't save JFK, Al says that Ziggy thinks "you were here to save her," referencing to someone off-camera. The shot cuts to Jackie Kennedy in her iconic pink outfit from that day, looking into the room her husband is in. "Your swiss-cheesed mind probably doesn't remember this," Al says, "but the first time, Oswald killed Jackie too."
At this reveal, Sam leaps.