“Superman and the Legion of Super-Heroes Chapter 4: Chameleons”
In the 31st century, Brainiac 5 has captured some of the Legionnaires including Superman. After dismissing the guards, he reveals that he's been trying to hold off an invasion of Earth by the United Planets. He also reveals that they have a plant who is close to the Justice League. The insider has tracked down one other captured Legionnaire, powering a machine. But she is discovered by Earth-Man and revealed to be Chameleon Girl. Brainy is discovered aiding the Legionnaires and must leave with them, which means without his interference, the war will start in four hours.