Do you believe time travel is possible? What about extraterrestrials? Or both? Computer specialist Joe Rebman joins a team to investigate what might be man's first contact with extraterrestrials. The alien nature of the craft, discovered at a remote location in the Arizona desert, raises concern for national security. This prompts the Pentagon to add Colonel Warren Anderson to the team. A group of college students on a field trip is discovered near the landing site. But they are not really students. They are time travelers from five-hundred years in the future with a mission to instigate the development of a worldwide genealogical database. 26th century doctors will use the data to track down and cure people with genetic mutations, saving millions from certain death. Is this an advance party of an alien invasion or time travelers on a lifesaving mission? Joe and the Colonel battle about which scenario is true. Joe believes he must help the 'students' save future humankind from genealogical doom. Colonel Anderson doesn't buy the story and wants to focus on the present. Who is right? THE YESTERDAY TREE asks fundamental questions about how we might respond to extra-terrestrial contact and confronts the possibility of time travel.