Forbidden Journey: When Worlds Collide

Earth was used as a dumping ground for alien prisoners in the past and DNA of human beings was altered because of it, thus creating the "evil gene." Forced to act because earthlings have introduced atomic weapons into space, a fleet of starships returns to earth to disarm them and to teach humanity the laws of the cosmos. What starts out as a riveting story about an alien starship's return to Earth in the near future goes awry quickly when the alien Commander falls in love with an Italian Scientist.

To further complicate the matter is a fleet of warships from another planet tailing the first contingent in a battle for Earth.