Jack and Susan are enjoying a much needed vacation, while their friends Paul and Janet are on their honeymoon in The Bahamas in the year 2002. Utilizing his time machine, Jack and Susan make a quick trip back home to the year 3012 to discover something strange has happened. The time line has been altered! When they get back to 2002, they are confronted by a pair of strange visits from people they never expected to meet.
Discovering the possible source of the events that altered the time line, they pitch in to help these new visitors. Once that problem has been handled to the best of their ability, they return home to 3012. However, once there, they come under attack by two opposing government forces. Ultimately siding with one of them, they find themselves in a battle for their lives.
Along the way, they meet new friends and become reacquainted with old friends. They travel to places and times they had only ever dreamed about encountering dinosaurs and even a fire breathing dragon!