This two part story is very similar in concept to a story told in Action Comics 761, whereby Wonder Woman and Superman have to spend a thousand years together on their own batting a savage horde of creatures in an alternate reality. To their friends and loved ones however, only a brief moment in time has actually passed between them departing and returning. That story explored how their feelings towards each other would develop and how loyal Kal would be to Lois, and this Batman issues seems to explore very similar territory.
Wonder Woman uses the Bat signal to summon the Dark Knight and tells him that The Gentle Man as been in contact with her and has asked to take them up on an offer they made him a while back, to temporarily take over the burden of fighting the Hordes of Gehenna so that he can take a rest. Apparently he has been fighting the creatures for centuries with no rest, in a never ending struggle.
Wonder Woman and Batman had come across him years ago on a Justice League Mission and had made the offer before being transported back to their own reality by Zatanna.
So as Bruce prepares to travel though the portal, Catwoman asks why he should go and not Superman. Bruce explains that he and Diana are the best fighters and this task is about more than brute strength.
And so the to heroes travel to the portal as The Gentle Man arrives in our world for rest and recuperation. As days turn into months, months turn into years for Wonder Woman and Batman as they have to fight a never ending wave of creatures day in day out. Meanwhile only a few hours have passed back on Earth as Selina helps The Gentle Man to look for his wife, whom he had left behind when committing his life to fight the hordes.
For Wonder Woman and Batman, during abreif respite, they begin to wonder if he will ever return to relieve them and that this may end up being their life forever. All they have left for consolation is each other. They lean in towards each other appearing to be about to kiss…