Justice League of America, Vol. 1

A meeting of the League aboard their satellite is abruptly brought to a halt when five of the members suddenly vanish, reappearing in space above Earth-Prime. With Green Lantern helping them, they manage to land safely in New York and eventually travel to the offices of DC editor Julie Schwartz. Flash uses the comsic treadmill he built during his last visit here but a powerful force prevents him leaving Earth-Prime.In Australia, a gang of poachers are stopped by a being called Ultraa who has amazing powers. The last survivor of an alien race, Ultraa was originally intended to be cared for by an automated robot called Maxitron. Unfortunately the robot was damaged and after coming into contact with an explorer, absorbed him and sensed the Leaguers' powers. Believing them to be allies of Ultraa whom it has decided to destroy, it flies to New York and attacks the League.Meeting with Ultraa, he and the League confront Maxitron and defeat it. Upon discovering it is Ultraa's presence that is preventing the League from leaving, the sole superhero of Earth-Prime decides to leave with the League for Earth-One.