Gruff, hard-nosed new boss Stanton takes over a scientific research company upon the death of his benevolent father. Scientists Manning, Gordon and White, who are very close to a breakthrough in time travel, are told by Stanton they must have results in 24 hours or face a funding cut-off. Trying to push their equipment past its safe operating limit they travel into the far future and distant past, with Stanton along as an accidental participant, unaware that a surprise awaits them as they struggle to return to the present.

Dr. von Steiner and his assistants, Mark Manning and Karen White, demonstrate their unfinished time capsule to Stanton Jr., the heir of their research center's founder. The machine breaks down, and all are thrust into the future (6968 A.D.), to discover a totalitarian Earth under attack by alien laser beams. They escape in the capsule but are hurled back to the year 1,000,000 B.C. Their attempt to ward off an assault by a prehistoric beast results in the destruction of the ruby that provides the time capsule's power. The three men find a volcanic cave filled with precious jewels that will enable them to return to the present, but von Steiner stumbles to his death in molten lava. Stanton flees in the capsule with a fortune in gems, but not fully comprehending the controls, he is killed. With the reappearance of the machine in their situation, Mark and Karen use it to return to the present, accidentally reaching the research center a day earlier than that of their departure. Anticipating that their fate will be that of Stanton, they depart in the capsule for a timeless journey.