Alright, going to do a long story short on this one because we all sort of figured it out already, didn't we?
So Mother's plan is to release an airborne virus of the St. Dumas ithycialamalanadingdong thing, basically controlling all the infected kids of a certain age range. Oh darn, everyone is at the Spyral school for teenage girl assassins, whoops.
And then we get to the meat of it, yeah, Cassandra killed Harper's mom. Harper was going to be the Robin mother selected, but Cass failed her mission and Batman wasn't ever working for Mother anyways, so Harpers life just sort of gets botched and Mother takes a cyanide pill, leaving Batman with the general notion of "dude, tried to mess with this people, you fucked up, this is actually all your fault."
I actually like this issue for a number of reasons. Say what you will about Harper and whether or not this was planned from the start or whatever, but this gives her a truly interesting origin, given how Batman really is to blame. That's another thing, this is one of those stories where Batman truly loses. There's no villain logic trying to spin it as it's fault but not really, no, Mother spells is out, he tried to play the game, he put it all in motion, he fucked up, Harper's life is on his hands. We don't get many stories where Batman is truly at fault like this, so it's nice to see some vulnerability in his character like this every now and then.
God though, the art takes a dip in those last four pages. There's another artist who isn't even listed in the credits, and I wouldn't be surprised if it is intentional, because some of those faces on those characters are fucking rough. Granted, this could be due to a demanding weekly schedule and DC needed some pages quick, but this brings me back to the point that I had made earlier: This book fixes Batman Eternal's narrative issues, but visually, it is subpar at best as a whole.