The aliens seen launching their attack in the last issue of JLA: Year One have enacted a systematic plan to rid the Earth of all its super-powered champions. Starting with Superman, it was all downhill from there: we see the aliens kidnap The Atom, Hawkman, the Metal Men, Johnny Quick, Dr. Mid-Nite, The Blackhawks, all of whom find themselves in:
The JLA tries to fight off the rampaging Appellax champions in Metropolis, but they are simply outmatched. Making a tough decision, they abandon the city and move on to Midway City, which they hope they can hold:
The team learns that Vandall Savage and his team used the Martian Manhunter's dossiers on all of the Earth's superheroes to figure out just how to attack them. Aquaman learns from his finny friends that their fellow heroes are being held prisoner, and where. The Flash formulates a plan which involves allowing themselves to be captured by some of Appellaxians, and taken to the gulag.
It's there that their plan is revealed: by disguising themselves as each other, they free the shackles placed on them by the Appellaxians and return the kidnapped heroes' weapons:
Waid's characterization of Aquaman continues to evolve, in this issue he's still a fairly serious dude but he can kid around a bit and seems to genuinely like his teammates. Bonus points for the Fish Intel, too.