Back There

"Back There" is an episode of the American television anthology series The Twilight Zone. On April 14, 1961, Peter Corrigan feels faint after a discussion of time travel with his friends at the Potomac Club, and finds it's April 14, 1865, the day of Abraham Lincoln’s assassination. He rushes to Ford's Theatre to warn everyone, but is arrested. After being kept in the police station and released in the custody of the assassin (posing as a Mr. Wellington), Peter realizes he was too late, and unable to change the past. He returns to the present; at the club, he finds that one of the members, a club waiter when he left, is now a wealthy man. When asked, the man reveals that he inherited his wealth from his great-grandfather, a policeman who had been the only person to believe Peter and made a name for himself trying to stop the assassination. full article at wikipedia