We pick up with Martian Manhunter who's been trying to come to terms with a period of his life that he's comfortable with. When he was a child he was tortured as a child by Lionel Luther and experimented on so the Legionares could weaponize his Martian physiology. Lionel Luther once again has him under experimentation but Martian Manhunter is extremely strong and easily free's himself.
It turns out it's just a robot and the real villain is doctor Ivo and his greatest creation known as Amazo.
The Justice League arrives on planet NIL the home of the monitors. I say monitors because after every crisis there's always a version of the monitor there to stop it and there's been a lot of different crisis events that have affected the multiverse. The prime monitor has been working over time to save the multiverse as he cares the most about it as after viewing it for so many millennia he has come to care deeply for it.
The Monitor agrees.
Back on Earth Dr Ivo is trying to dissect Martian Manhunter in order to continue Lionel Luther's work to create an apex predator of both human and martian as Amazo is nothing more than a feeble servant at the moment. That's the only reason Ivo is working for the Legion of Doom anyway. Luckily Hawkgirl intervenes and proceeds to lay the smackdown on the Amazo androids that Ivo has had stacked up. I mean they've adopted their son from another universe... you can't get around that. *cough* they escape but with a warning from Lex Lutho