Plot summary
Lois and Clark know that Leslie ( Patrick Cassidy ) is in reality Lex Luthor's son and Leslie, to prove them that he is not like his father, reveals to everyone who he is and that he will try to fix everything his father destroyed. It is revealed that the real Lex Luthor Jr. is in fact the man who appears as Mr. Smith (Keith Brunsmann). Lex Jr. is in love with Lois and wants to separate her from Clark. He makes a device with which he controls Lois' head and causes her pain if she does not do whatever he asks.
Lois leaves Clark and asks him for a divorce while at the same time leaving him a note that she is in danger. Lois is kidnapped by Lex Jr., who tries to make her love him, while Superman is searching for her. He finds them and when Lex Jr. tells him what he wants from him, Superman freezes Lois making her look dead. Leslie helps Superman to save Lois while he and Lex Jr. stay behind and get killed by the bomb that goes off. In the midst of all this, Superman tries to find out, with Dr. Klein's (Kenneth Kimmins) help, if he can have kids. Note: John Shea makes an uncredited appearance as the voice of Lex Luthor in the episode recap. This is his final ever appearance of the role in any form.
Credits
Adapted from Wikipedia contributors, Lois & Clark: The New Adventures of Superman season 4. HTML formatting and reference markers removed.