The first spaceship to Mars rounds the Red Planet and heads back toward Earth but runs into an unexplained phenomenon in space that accelerates the craft to such a high speed that all four men aboard black out. When they awake, they've crash-landed on a planet that they only gradually realize is Earth -- of the distant future: they have crashed through the time barrier. After they are chased by ugly "Mutates," they are taken in by the declining remnants of human civilization who live underground. It's now 2508 A.D, almost 400 years after an atomic war almost wiped out the human race. John Borden (Hugh Marlowe) falls in love with Garnet (Nancy Gates), daughter of Timmek (Everett Glass), leader of the underground people -- a fact that enrages Mories (Booth Colman), who's always assumed she would someday be his. The scheming Mories tries to turn his people against the space/time travelers, but falls victim to his own nefarious plans. Learning from Deena (Lisa Montell), a servant girl from the surface of Earth, that most people up there are normal though cruelly ruled by the deformed ones, Borden and his friends take on the mutates with modern weaponry and reclaim the Earth for normal humanity.
Although this is (surprisingly) the first American feature film to deal with scientific time travel, World Without End is really just another lost-civilization plot, complete with princess, evil grand vizier, and lots of skulking in corridors. There are few imaginative touches -- the giant spiders in particular are pathetic -- and some of the cast isn't very good. But for the period, this is slightly above-average science fiction; the exteriors, shot at the famous Iverson Ranch, have an open, fresh feeling, but the interior sets are unimaginative and routine. The plotline owes more than a little to H.G. Wells' The Time Machine (a lawsuit was filed), which makes the presence of Rod Taylor in the cast (as the hunk from our time) a little ironic, as just a few years later, he starred in George Pal's much-loved movie version of the Wells novel.