An alien race, the Kanamits, come to Earth providing technology and guidance to turn the planet into a utopia. But one man questions their benevolence.

When parents Chris and Ruth Miller wake up in the middle of the night to the cries of their daughter Tina, they are shocked to discover that she somehow fell through the wall of her bedroom into another dimension. They then call Chris' physicist friend Bill for help in rescuing Tina before the portal she fell through closes for good.