[Takes place after Justice Society of America]
After her mother marries Patrick Dugan, Courtney Whitmore finds the Cosmic Staff belonging to the late Starman from the JSA, in her mom's husband Pat's basement, he reveals to her about the Justice Society of America (Earth 2) and how he was whisked away to Earth 1 to save him life, Pat was the only survivor. When Courtney holds the Staff, it glows, only for her. Courtney believes that she must be Starman's daughter because her dad that passed away years ago looks like Sylvester Pemberton and that is why the Staff works for her. She decides to continue Starman's legacy as Stargirl, Pat decides to be her sidekick S.T.R.I.P.E. after she refuses to give up the Staff (Pat was Starman's sidekick in the JSA on Earth 2). Pat discovers that the ISA (Injustice Society of America) also exists on this Earth (Earth 1). They confront two members of the ISA, Icicle and Brainwave.
Meanwhile, Courtney goes off recruiting for new members of the JSA.
[Post Credit Scene: With Brainwave in a coma after the final battle, Jordan (Icicle) assembles the 'remaining' ISA again for a meeting.]
