Supergirl and the Legion of Super-Heroes

The Legion of Super-Heroes searches for the missing teammates and finds them with the help of Supergirl's enhanced senses. When they arrive to return them back, they find that the kidnapper was a group called the Wanderers and they are being led by Lightning Lad and Light Lass' brother, Mekt Ranzz. Mekt Ranzz explains that they are working independent of the United Planets and he didn't kidnap the Legion members, he wanted to recruit them to his team. In the middle of this, they all get word that there is a machine uprising in Megatoyko. Supergirl, Brainiac 5, Ultra Boy and Mon-el race to Megatokyo to stop the revolt. It seems too simple at first until a giant robot rises from underground, shaped like a giant Dominator. It's mostly hollow and Brainiac 5 realizes that is is housing a red chemical. It releases the chemical, making it visible from outer space.