"Back There" is the thirteenth episode of the second season of The Twilight Zone. It starred Russell Johnson, most famous for playing The Professor on Gilligan's Island, as Peter Corrigan, who is also a professor. This is the second episode Johnson would perform on on The Twilight Zone, the first being The Execution, in which he also played a professor.
Corrigan is talking with some of his compatriots at an exclusive club in Washington, D.C. about the possibility of time travel and changing the past. What seems to be an idle discussion turns into a vital question when Corrigan, heading outside, finds himself mysteriously transported to 1865 on the eve of Abraham Lincoln's assassination. He desperately tries to warn people about the upcoming assassination, but it might be that history can not be rewritten. As in many Twilight Zone episodes, there are two endings: the regular ending, and then the twist ending.
Much as with the other Johnson episode, I was a bit unclear about what the moral of this story is. Perhaps that if I ever get transported back in time and have to warn people of a catastrophe, I should come up with a more plausible line than "I can't tell you why, but you have to believe me." Otherwise, I find it an interesting note that this might be one of The Twilight Zone episodes that could share continuity with another episode: perhaps after Peter Corrigan goes through the events of this episode, he devotes himself to the study of time travel and later (with a name change) is the same professor portrayed in "The
Execution".