This occurs as the last series of scenes in this chapter before we jump back to the wolves at the campfire. This scene happens right after we end Vox's point of view where he is on the surface with Wrex and sees the eyes of the foxes appear in the woods.
We see Vox ordered back into Wrex's room, watching the rabbit read and re-read a letter. Eventually Vox says something like "You called me sir?", tired of waiting. Wrex looks up like he forgot Vox was there, and hands him the letter. Fecs is also in the room.
The group discuss the letter, with Wrex admitting this could change everything. It's a letter they were given by one of the foxes, clandestinely. Vox reads aloud that apparently Marathon, one of their cities, has been inhabited by rats, and the rabbits are invited.
We need to think about why Pascal needs the rabbits, he wants to open up some deeper part of the city but there aren't any rabbit espers...so does that still make sense? Wrex could always decide he's going to Zarkhan when he takes over.
As they discuss the implications, Fecs mentions that they will need to use their 'asset' to open the gate. Wrex looks up and says he wants to 'see it'.
We transition into an elevator scene with Wrex and Vox, as they go down to the prison cells where Muts is located. They are talking in Lapine and they refer to Muts as a 'wolf' at several points, but we leave in the untranslated word for wolf, which is part of the controversy behind Foxmilk's translation, as some argue that you are meant to know that Muts is a wolf by this point in the story.
They have a discussion where we see there is already some tension with Vox commenting on how often Wrex comes down here. Vox references how he found Muts staring at a spot on the floor, well actually, it was someone else who initially found him, but Vox made that person swear to secrecy. Wrex asks about that person and decides to have him reassigned to be closer to him so he can keep an eye on this person. (They already had this conversation, the elevator ride is about them re-touching on these previous points to inform the audience and show the subtle tension between Wrex and his subordinates.)
The conversation turns to how Muts got out. Muts admits he left the cage unlocked, but says it shouldn't matter. Vox asks why and Wrex says because the elevator should never have come down there to begin with. He suspects a spy, but Vox offers the possibility that Muts somehow called the elevator himself, if his esper abilities are manifesting. This possibility disturbs Wrex.
They continue talking until Wrex gets to the cell, he tells Vox he can leave. Vox hesitates, saying that Wrex shouldn't be alone with it if it's manifesting esper abilities. Wrex says don't be ridiculous, Muts is only a child. Vox leaves but the tone of the conversation leaves a bad taste in Wrex's mouth. He enters the cell alone.
Maybe earlier in the scene Vox spies Wrex surreptitiously packing a book in his Satchel for Muts, the same book he brings out for Muts now. Furthermore Muts as working on sewing up the collar for Muts when Vox first arrives (early, Wrex notes) before they bring out the cargo for the foxes.
During this scene perhaps Vox says when he saw it so still in its trance, he was hoping perhaps it died. Wrex replies it will outlive them all.
The cell is dark and dim like before, Wrex moves over to a aether furnace to turn up the valve.
Muts (yelling out from the darkness, angry and hurt): I want it off!
Wrex ignores this order and turns the knob, light floods into the room, making Muts squint, he's still huddled up in a corner.
They have a conversation, where Muts is like an angry child having a tantrum, and Wrex is like a stern parent or principal. But the conversation quickly softens, as Muts is happy to see Wrex, and Wrex has a new book for him. Wrex gives Muts the collar telling him to be more careful, and when Muts complains about Vox Wrex says he's doing his job and notes that 'Vox' is Foxlish for child, although Muts says he can't imagine Vox was ever a child. It's late and Wrex says he needs to sleep soon, but Muts begs and convinces Wrex to read the book he brought for Muts, and Wrex concedes. The truth, we can tell, is that they're both quite fond of each other, and Wrex enjoys spending time with Muts, despite Muts supposedly being a prisoner.
Their casual conversation, which clearly violates the formal relationship between prisoner and guard, is disturbing to Vox, who we see is actually behind the door, and has covertly been listening to the conversation the entire time. Hinting that he's starting to question Wrex's judgment as a superior officer. As we see later in this story arc, he's not the only one.*