The plot involves quantum physicist Sam Beckett leaping into a variety of different people in various points in history within the time span of his own lifetime. His only link with his own time is the cigar smoking, womanizing Al, who appears to Sam as a hologram that most people other than Sam cannot see or hear.
The show overlaps a number of genres, including science fiction, family drama, comedy, social commentary and nostalgia, thereby acquiring a broad range of fans.
At the end of each episode, Sam leaps into another person, giving viewers a teaser of the following episode's leap. As part of a running gag, after Sam's leap, in awe or dismay about his new situation, he often utters the catch phrase "Oh boy!".