The Original Series Premise              

"Theorizing that one could time-travel within his own lifetime, Dr. Sam Beckett led an elite group of scientists into the desert to develop a top secret project known as Quantum Leap. 

He awoke to find himself in the past, suffering from partial amnesia and facing a mirror image that was not his own. 

Fortunately, contact with his own time was maintained thorugh brainwave transmissions with Al, the project observer, who appeared in the form of a hologram that only Dr. Beckett can see and hear.

Trapped in the past, Dr. Beckett finds himself leaping from life to life, putting things right that once went wrong and hoping each time that his next leap would be the leap home."