Xartan Warlord Ugarth and his son Zano intend to conquer Earth. Using their power to change form into any being, the Xartans are replacing influent people in the city to create chaos and panic so that when they invade the planet, its inhabitants will be too disorganized to oppose them. But their plan is thwarted when they come face-to-face with Thor. Zano uses several forms to attack Thor, but he is unable to defeat the Asgardian. Then his father tries to engage him in singular combat by making himself invisible. When Thor grabs the warlord and hurls him into space, his fleet decides to go after him and abandon their project. Thor decides to keep Zano and his companions as hostage to dissuade any retaliation from the Xartans. Then he orders them to change into trees, knowing that trees will not have the intelligence to turn back to their original forms.