Corrigan (Russell Johnson) is a wealthy man in an exclusive club in Washington. The subject of time travel comes up, and before you can say 'not-on-my-watch' he finds himself in 1865, the night of President Lincoln's assassination.
As you know from so many film and TV dramas the course of time travel interfering with assassinations never did run smooth. There's a twist at the end as well as a halfway twist. An enjoyable Zone but the production is slight. One of two time-travel tales with Russell Johnson (Execution, series one), both good.
Serling returned to the subject of historical assassinations in 'No Time Like The Present' (series three) where a time traveler contemplates preventing the shooting of President James Garfield, on finding himself in 1881. In series five Serling reacted to the killing of John F Kennedy with 'I Am The Night Colour Me Black'.
Before this was made there was an episode of 'One Step Beyond' where Lincoln dreams of his death very shortly before it happened. More or less true according to the writing of a bodyguard and legal partner of Lincoln, Ward Hill Lamon.
There was a film directed by Anthony Mann in 1951, 'The Tall Target' in which Dick Powell played a police detective called JOHN KENNEDY trying to stop a plot to kill Lincoln at the time of his inauguration in 1861.
In 1990 there came an interesting but little known film concerning trying to stop Kennedy's murder by time travel called 'Running Against Time'.
The final series of 'Quantum Leap' had a two-part story about taking over Lee Harvey Oswald's body to try to change events.