Future Boy was the 13th episode of 3 of Quantum Leap, also the 44th overall series episode. Written by Tommy Thompson, the episode, which was directed bu Michael Switzer, aired for the first time on NBC-TV on March 13, 1991.
Sam leaps into Future Boy, the sidekick of 50's TV superhero Captain Galaxy. Al informs Sam that Moe Stein (played by Richard Herd), Captain Galaxy, is mentally unstable and that Sam is there to have Moe committed to prevent him from accidentally killing himself while trying to hop a train. Therefore, it initially looks like Sam has to help Moe's estranged daughter Irene get him put into a mental hospital as he is a danger to himself.
Sam doesn't think Moe is unstable and he feels that he is there for another purpose and that having Moe committed is not necessary. After talking to Moe, Sam learns that he is building a time machine and that Moe's theory of time travel is an incomplete version of Sam's own String Theory, which was the basis for Project Quantum Leap. Sam shares the rest of the theory.
Sam represents Moe in a mental competency hearing, but Moe loses and is sentenced to a mental hospital. Before he can be taken into custody and committed, Moe escapes and races back home to try his time machine, the Time-o-nometer. At first it looks as though Moe is going to Leap the same way Sam does, but the machine doesn't work.
Moe explains to Sam and Irene why he wanted to travel in time; when Irene's mother discovered she was pregnant, Moe was ready to give up acting and settle down. However a rave review he got for a theatre performance caused him to be inundated with job offers and Moe, feeling a duty to provide for his family, took them and spent much Irene's life on the road. Moe now regrets not having been there for her and wants that time back. Irene tearfully forgives her father, and decides not to send him to the hospital.
Moe decides to move in with Irene, bringing Captain Galaxy to an end. Al tells Sam that Moe has a happy retirement living with Irene. At the end of the final episode, Captain Galaxy responds to one last reader letter (sent by none-other than a young Sam himself) and explains his theory of time travel that now includes what Sam shared earlier. Before Sam can react to this, he leaps.