WhentheVikingspacecapsulesuddenlyreturnstoEarthfromitslongagotriptoMars,itbringswithitanintelligentvisitorthatispart"Alien"andpart"ET".Encasedinarmor,itextendsahumanlikeformfromitsshelltoexamineitssurroundingsandshowsaninterestinhumansincludingasoftcaressofafemalescientistpriortotheArmykillingit.Thisonlyenragesitssibling.