Be forewarned, this episode has a LOT of blood. [ *shudder* ]
The episode unfolds by recounting the final moments from the previous episode. However to keep things fresh it adds in a flashback from Zack’s perspective.
We see that in the event from Zack’s past (where he had to dig a hole in the backyard to bury another child), Zack discovers a bare skull buried deep in the wet ground. Upon returning inside Zack sees that the male caretaker has left a murder movie playing on the TV, and Zack watches a young couple get murdered by a knife-wielding maniac. This scene gives Zack the idea of how to kill his caretakers, which is exactly what he does.
Back in the present the drugs Zack injected himself with begin to take over his mind again, forcing Rachel to backtrack down the tunnel in order to save herself. She finds herself in a large room with 4 machine guns attached to the ceiling, and a wall of clear plexiglass blocking the exit. Cathy emerges and shoots Zack twice with the guns, trying to use pain to temporarily clear his mental state. Cathy gives Rachel a gun and tells the two kids to kill each other.
Rachel refuses. She tells Zack that they should not allow themselves to become tools to be used by Cathy, and that they have the right to choose whether or not they want to kill or die. So Rachel chooses to not kill Zack, but is accepting of the idea that he may choose to kill her. Zack gets so wound up that he slashes his stomach open with his scythe.
Seeing Zack die pushes Rachel closer to some kind of psychological edge. Cathy is so angry that Zack denied her the pleasure of killing him that she emerges from behind the plexiglass wall to berate Rachel to failing to kill Zack. Cathy is about to kill Rachel with the ceiling-mounted guns when Zack suddenly starts gasping and twitching on the floor. Zack’s alive! But how…?
It was really difficult for me to watch Cathy, a full fledged sadomasochist, hurt Zack as he lay on the brink of death and bleeding out on the floor. Rachel has difficulty watching as well, and it’s this cruelty from Cathy which pushes Rachel over the edge. Rachel pulls a loaded handgun from her bag (because Cathy’s gun was fake and unloaded) and shoots Cathy in the abdomen, saying that she’s not allowed to kill Zack because Zack’s the only one allowed to kill her.
Cathy is wounded and distracted enough that she doesn’t notice Zack regain consciousness, allowing him to sneak up on her and kill her. Because Cathy left the plastic wall parted in order to approach Rachel, Zack and Rachel are now able to escape. They make their way to the elevator and ascend up to B2.
In the elevator Zack praises Rachel for being able to shoot Cathy so coldly. We also learn a little about Rachel’s backstory. Apparently 
she came to the facility for counseling after seeing someone get killed, but she “woke up in a room with a blue moon.” But Cathy called both Rachel and Zack criminals, so if Rachel really did commit a crime, what is she leaving out? Did she shoot someone else, maybe her therapist? Her parents?
Just as the duo reach the second floor, Zack topples over and starts to bleed all over the floor of the elevator. How will Rachel be able to save him? Is Zack unable to die despite sustaining mortal injuries?
This was a somewhat slow episode, and as someone who’s not a horror fan and doesn’t do well with blood, the majority of this episode made me squirm uncomfortably while watching. I guess this means Satsuriku no Tenshi is doing something right, no?
I’m glad we got a snippet of info about Rachel’s past, but each revelation just gives me more questions and leads me to want more information. I also still want to know why Cathy knew so much information about Rachel and Zack’s pasts; did she know them personally or did someone higher up the ladder give her information on them? Who is the mastermind behind this entire labyrinth?
On a final note, I think my favourite scene was Rachel discovering the verse written on the wall, and then using it to get herself and Zack onto the elevator. I thought it was interesting that she kept its meaning from Zack, who seemingly doesn’t know how to read (although if you consider that he was an abused child raised in a home environment that was definitely NOT nurturing, then this makes sense). When it comes time to insert the namecards into the slot on the wall next to the elevator Rachel chooses Zack’s name, implying that she’s the sinner who “God does not need.” I wonder what Rachel did that was so horrible that she’s somehow a worse criminal than Zack, who actually killed two people. Ahhhh, so many questions…. x_x
Kill two people? Zack is a serial killer who kills a whole lot people before becoming a floor master. I’d be surprised if what Rachel did is beyond what he did. Since Zack and Danny knows each other, and Eddie and Cathy knows Zack too, it can be assumed that all floor masters knows each other even if it’s only by name. Maybe at the very least, they all met once briefly before the story (the manga has yet to explain how they know each other too). Since Cathy seems to know Zack even before he came to her floor and is rather obsessive of him, I can only think that she did a digging of her own about her favorite sinner/criminal.
Sorry, I forgot about the first couple of episodes. Was referring to his caretakers from his memory. Your theory makes sense.
well, Catherine….it was nice knowing ya…