Faced with the sudden alien invasion, the earth's army was vulnerable, and the governments of various countries collapsed. Six months later, only a few people on earth survived. In order to drive away the aliens and rebuild their homes, these people rose up to carry out various resistances. Tom Mason (Noah Wyle) was originally a history professor. His family was broken up because of the alien invasion. He joined the resistance corps with his three sons and tried to fight against the aliens. The aliens have been robbing human children, putting armor on them and turning them into their slaves. In addition to dealing with the aliens, the resistance corps must also try their best to rescue these controlled children. However, due to the disparity in force, the resistance corps has been at a disadvantage, avoiding the pursuit and interception of aliens everywhere. Until one day, one of the resistance army developed a bullet made of alien mecha, which can effectively penetrate the alien mecha and give the aliens a fatal blow. At this time, the resistance corps saw that the force was slightly tilted towards them, so they planned to launch a surprise attack on an alien stronghold...