Wonder Woman, Superman and Batman rush to the scene of a massacre at the Sanctuary, a refuge created by the Trinity for heroes to recover from the trauma and stress of their roles.
As they investigate the site which is strewn with the dead bodies of various heroes, a fight is breaking out at a diner elsewhere as a manic Harley Quinn attacks Booster Gold unprovoked, stabbing him several times. As the two of them scuffle they eventually take the fight out into the countryside and finally come to a stand-off.
It is revealed that both of them had also been members of the Sanctuary but when Booster Gold asks of Harley why she had been responsible for the deaths of the others and she replies that while she had not saved them she had not killed them either. It had been him.