A Leap for Lisa

A Leap for Lisa is the season finale for season four of the television series Quantum Leap; it tells the story of Sam leaping into a younger Al.

The dream starts with Sam leaping into a young man who is alone on a beach with his lover. This, however, turns out to be a mislead, when Sam wakes up and discovers that he has leapt into his newest host in the middle of a dream.

Sam's host, a young naval recruit nicknamed "Bingo," has a loving girlfriend and is popular with his peers, but he is also a minor suspect in the death of a superior officer's wife. Despite having had a brief affair with the woman, Bingo has an alibi; on the night of the murder, he was with his girlfriend Lisa (guest star Terry Farrell), a nurse serving on the naval base.

Lisa is eager to prove Bingo's innocence despite the fact that her career might be ruined by the revelation that she had been dating a naval recruit, which is taboo on the base. Sam assumes that he is there to prevent Lisa from ruining her career, and discourages her from telling anyone about the alibi, figuring that since he is only a minor suspect, he will find some other way to prove his innocence.

After an unusually extended absence, Al finally arrives, and reveals that "Bingo" is actually a younger Al Calivicci; Al accounts for his delayed appearance by explaining that he had been thrilled to encounter his younger self in the Waiting Room.

At first, Al and Sam are both highly amused by the synchronicity of the leap, but when Al learns of the date, he realizes too late that Sam has leapt into his younger self to prevent Lisa from dying in a car accident. Al is devastated, revealing Lisa to be his first true love.

Furthermore, Sam learns that, in the original timeline, it had been Lisa's testimony that had prevented Al from being accused of murder. Now that the only witness for Al's alibi is dead, Commander Riker -- Bingo's superior officer and the husband of the murdered woman -- fingers Al as the murderer, and Bingo/Sam is given a court-martial; if found guilty, he will be sentenced to death.

Sam's investigation to find evidence of his innocence is hindered when he is put under constant guard, and after devastating testimony from Riker -- who seems to honestly believe he saw Al murder his wife -- Al disappears from the future and is replaced by Edward, a more formal project observor, played by guest star Roddy McDowall. As the only person who remembers that Al had ever been project observor, Sam realizes that Edward's appearance indicates that Al had been found guilty and executed in the new timeline, due to Sam's interference.

Sam continues his investigation, avoiding imprisonment during the trial due to Al's stellar military record. With Edward's help, Sam manages to prove that one of Al's buddies was the real murderer, and had been mistaken for Al because he had been wearing Al's uniform. Edward disappears and is replaced by Al, who is oblivious to having ever been wiped from existence.