Stanton (Scott Brady) is a grouchy boss who is the head of a scientific research company. He has taken over the company following the death of his father. His employees are scientists Mark Manning (Anthony Eisley), 'Doc' Gordon (Abraham Sofaer), and Karen White (Gigi Perreau). Unless they prove that their time travel experiments can produce some results, their funding will be cut off.
Desperate, they push their operating equipment past the level of safety and travel 5000 years into the future. There, they encounter aliens led by Vina (Poupe Gamin) who are looking for a planet to colonize. The aliens find no welcome on Earth, which is in the midst of a global war that threatens the human race. She urges them to go back and warn humanity about the danger, then dies in a human attack.
The time travelers retreat to their chamber and head back. On the way, they detect another time machine on a collision course. Gordon tries to communicate with them; when that fails, they fire at it, but their weapon is too weak. Stanton takes charge, boosts the power and destroys the other vessel.
However, all is still not well. They overshoot the present and end up in the distant past, in the age of dinosaurs. Their giant ruby, a key component of the machine, is destroyed, leaving them stranded. However, when they explore a nearby cave, they find it studded with all sorts of jewels, including rubies.
Overcome by greed, Stanton grabs handfuls of the precious gems, returns to the time machine, replaces the ruby and takes off without the scientists. However, on his return trip, he encounters another traveler in time. He hears a radio broadcast - it is from Gordon! He is racing towards the earlier version of the time machine. Then he is destroyed by a blast initiated by his earlier self.
Meanwhile, as the scientists leave the cave, Gordon stumbles and falls to his death in molten lava. The other two find the time machine gone. Then it mysteriously reappears. They board it and return to the day before their initial departure. But something is wrong; they find past versions of themselves living at a much slower time rate. The couple hasten back to the time machine to try to rectify the problem, but end up hopelessly lost in time and space. In the final scene, the machine is shown in space among the stars.