Professor John Oldman is packing his belongings onto his truck, preparing to move to a new home. His colleagues show up to give him an impromptu farewell party: Harry, a biologist; Edith, an art history professor and devout Christian; Dan, an anthropologist; Sandy, a historian who is in love with John; Art, an archaeologist; and his student Linda.
As John’s colleagues press him to explain the reason for his departure, he picks up from a reference to Magdalenian cultures by Dan and slowly, and somewhat reluctantly, reveals that he is a prehistoric caveman himself from that precise period. He states that he has lived for more than 14 millennia, and that he relocates every ten years to keep others from realizing that he does not age. He begins his tale under the guise of a possible science-fiction story, but eventually stops speaking in hypotheticals and begins answering questions from a first-person perspective. His colleagues refuse to believe his story but accept it as a working hypothesis in order to glean his true intentions. John relates he was a Sumerian for 2000 years, later a Babylonian, and eventually went East to become a disciple of the Buddha. He claims to have had a chance to sail with Columbus (admitting that at the time he still believed the earth was flat) and to have befriended Van Gogh (one of whose original paintings he apparently owns, a gift from the artist himself).
In the course of the conversation, each guest questions John’s story based on knowledge from their own academic specialty. Harry struggles with how biology could allow for the possibility of a human being living for so long. Art, arguably the most skeptical of the group, questions prehistory. He exclaims that John’s answers, though correct, could have come from any textbook; John rejoins that, like any human, his memory is imperfect and he only sees events from his own narrow, hence not omniscient perspective. Dr. Will Gruber, a psychiatry professor who arrives at Art’s request later that afternoon, questions if John feels guilt for outliving everyone he has ever known and loved. He then threatens John with a gun (later revealed to have been unloaded) before temporarily leaving. John then learns from Harry that Will’s wife had died the previous day after a long illness.
The discussion veers to religion, and John mentions that he does not follow any. Even though he does not necessarily believe in an omnipotent God, he does not discount the possibility of such a being’s existence. Pressed by the group, John reluctantly reveals that in trying to take the Buddha’s teachings to the west, into the eastern Roman Empire, he became the inspiration for the Jesus story. After this revelation, emotions in the room run high. Edith begins crying. Will demands that John end his tale and give the group a sense of closure by admitting it was all a hoax, and threatens to have John involuntarily committed for psychiatric evaluation should he refuse to do so. John appears to ruminate over his response before finally “confessing” to everyone that his story was a prank.
John’s friends leave the party with various reactions: Edith is relieved; Harry and Dan indicate an open mind; Art never wants to see John again; Will still believes John needs professional help; Sandy and Linda clearly believe John. After everyone else but Will and Sandy have left, Will overhears John and Sandy’s conversation, which suggests the story could be true after all. John mentions some of the pseudonyms he has used over the years, and Will realizes one was his father’s name. He asks John questions that only a very close acquaintance could answer. When John answers them correctly, Will has an emotional breakdown, suffers a heart attack and dies in their arms. After the body has been taken away, Sandy realizes that (if the story is true) this is the first time John has seen one of his grown children die. John wordlessly gets in his truck and starts to drive to an unknown destination. Then he stops and waits for Sandy, who walks over to the truck and departs with him.