The current configuration of Justice League United find themselves on the run after they have been sucked into the gaping maw of, as the caption says, "A super-gross living island thing":
Part of the creature's ultimate plan is revealed to Swamp Thing, who communicates this to his "teammates." Then the living island starts to rise out of the water, heading inland. Mera again uses her powers to help the JLU escape:
The creature is destroyed, but so (seemingly) is Swamp Thing. Poison Ivy is aghast, walking off with Swampy's head in an attempt to revive him (which will probably work). With the mission now completed, Mera demands what she was promised--namely, to find out where Aquaman has gone. Animal Man promises to return her to his last known location--meanwhile, Star Girl is busy rounding up members for a new mission. And she's starting with Batgirl!
I have to say, I was pleasantly surprised to find that this story wrapped up in just two issues! After what feels like decades of superhero plots being stretched past their normal life span so they fill a trade, I like Jeff Parker's approach here--if anything, it felt a bit like those JLA/JSa team-ups of old, which generally ran two issues at best and then got out of town.
From what I understand of this book, the team will be ever changing, so I guess that means Mera will not be returning for issue #13. Too bad, because it was great seeing her sans-Aquaman and kicking so much ass. She's not exactly team leader here, but it's close, and her powers end up saving the heroes more than once. Parker has found a good balance on how to write Mera, so let's hope Adam Strange and co. need her again, soon!