Plot summary
Clark keeps having nightmares about losing Lois seeing her going through a window and being unable to save her. In the meantime, a Utopian citizen named Andrus ( William Christopher ) comes from the future to take Tempus ( Lane Davies ) back to Utopia for his trial. Tempus manages to escape Andrus and steals the time travel window to come back to Earth. With a new identity under the name John Doe, he runs for President and manages to win the elections since he uses a subliminal device to control people's minds and make them believe that "John Doe Is A Darn Nice Guy".
Lois and Clark are the only ones who know Tempus and who he really is and they try to stop him. Andrus comes back and works with Superman but in their attempt to trap Tempus, Superman is the one who gets trapped in the time travel window and seems lost forever. Since Superman is gone, Utopia does not exist anymore and Andrus also disappears leaving Lois behind not knowing what to do and where Clark is and Tempus being the President Elect of the United States.
Credits
Adapted from Wikipedia contributors, Lois & Clark: The New Adventures of Superman season 4. HTML formatting and reference markers removed.