Time travel is not easy for Sam Beckett, especially when you can't control where you might end up next. As an added complication, leaping messes with your mind. Although Sam usually remembers who he is after a leap, parts of his memory get scrambled each time, making it difficult for Sam to remember previous leaps, skills he possesses, and information he may have already known about the current time period (the swiss-cheese effect). Sam is assisted by a support team anchored in the ``present'' (the late 1990s). Rear Admiral Albert Calavicci (Dean Stockwell) is the Observer and he's also Sam's best friend. A small amount of neural material collected from both Sam and Al allows Ziggy, the semi-sentient, hybrid supercomputer to track Sam through time. While he is in the Imaging Chamber, Ziggy can project a holographic image of Sam's time period around Al. Sam, in turn, can see an image of Al in his own mind. Through the handlink to Ziggy (a palm top data terminal) Al can provide advice and information to Sam which will help him determine the nature of his mission and then complete it.

Exactly what Sam is supposed to ``put right'' each leap often remains a mystery well into each episode. When Sam leaps, he trades places with someone in the past. That person ends up in the ``future'' in the Project's Waiting Room (often scared and confused) while Sam takes their place. People in the past don't see Sam Beckett, they see the person he is replacing. Small changes for the better in the lives of seemingly anonymous people will often have major repercussions on significant historical events in our recent past.

Quantum Leap was a successful television series. It ran for 4 and 1/2 seasons for a total of 95 episodes (including multi-part episodes) on NBC. During its run, Quantum Leap won numerous awards (5 Emmys and 2 Golden Globes) and enjoyed good ratings. The show was suddenly canceled by NBC after the end of season 5. Now the subject of great debate amongst its fans, the last episode of Quantum Leap, the infamous Mirror Image, was intended to be a season finale cliff-hanger. With the announcement of the show's cancellation well after the filming and much of the editing of Mirror Image was complete, the episode was hastily re-edited to turn it into a series finale. Although the episode was originally designed to address many outstanding questions about Sam's leaping, it raised many more new questions that it answered. Many fans were, and still are, unsatisfied with Mirror Image. There have been numerous requests over the years for a TV movie (or even a feature film) to bring proper closure to the series.

Quantum Leap can still be seen world-wide in syndication. The show continues to pull in new fans. Since its cancellation, over a dozen novels based on the series have been published and several non-fiction books documenting the series can be found in bookstores. Numerous fan clubs and World Wide Web sites devoted to the series show that Quantum Leap fandom is alive and well.