Using their time viewer, three scientists see a desolate landscape 107 years in the future, at which point the electrician realizes that the viewer has unexpectedly become a portal. All four jump through, only to have the portal collapse behind them, whereupon they are chased on the surface by Morlockish creatures who are afraid of thrown rocks, and they meet an advanced, post-apocalyptic, underground society that employs androids and is planning a generation-long trip to Alpha Centauri.

The film draws in at least four important additional time travel tropes: suspended animation, a single nonbranching, static timeline (with the corresponding inability to go back and change it), experiencing the passage of time at different rates, and a trip to the far future. And according to the SF Encyclopedia, the film was originally conceived as a sequel to the 1960 film of The Time Machine.