The plan is refined and strengthened, contingencies are set to deal with various ways Thorn could've strengthened his defences, Mortal receives a very interesting email concerning one of their mother's contingency plans—namely that her assets have all been either frozen or transferred to Mortal themself, so Thorn doesn't have access to them -, and when Mortal and Promise judge there's nothing more to be gained from further planning they (eat dinner, sleep again, have breakfast, go over the plan once more when it's not completely fresh in their minds so they see if they come up with anything new, purchase Promise a mobile phone and a power generator to charge its battery in fairyland, eat lunch while Mortal teaches Promise how to use that, and) part ways.
On this side of the veil, Mortal gets to work. The first step: getting at least two safe houses, one for their HQ and the other for contact with the place near Thorn's court. They end up getting five, for redundancy's sake. The main HQ is near Seattle, the other four safe houses are in Greece, Russia, Japan, and Argentina. That, and getting the necessary existing equipment, is the easy part—you end up with contacts of the relevant sort when the bulk of your wealth comes from the kind of thing you can get with sorcery. The hard part is getting the various specific bits of technology that don't exist yet, including the the many types of trap and ammunition they'll need. Processing fairy voices with software turns out to be a dead end—apparently they're weird magical superpositions of sounds that make software go ?!?!?!?!?—but everything else, as agreed upon, can be made to spec nicely enough.
It'll take a couple of weeks beyond the one month for everything to be ready. Mortal hires someone who talks very fast.
And after the ball's going, there's not actually much for them to do with their time. They fret about details of the plan, order more redundant pieces of stuff (especially the to-spec stuff, not being mass-produced means they'd better have a lot of it to start with in case anything goes wrong), and have various antsy and anxious and calm and relaxed and terrified and panicked moods. A month is a long time...
At one point it occurs to Mortal that Promise might've decided to run away and not help, and then they'd never see her again and that would be terrible, and why would it be terrible anyway? It's just some fairy, fairies are evil, one must remember that. Even though she wasn't, of course, she was smart and resourceful and moral and ridiculously hot, and if they never see her again she'll never order them again and the tingly feelings won't ever happen again. Except what the heck, what are they even thinking? The answer, of course, is that they want to see Promise again. Why? To save their mother, of course. The only reason being ordered like that felt good was because Science. Of course. Of course.
The month passes—
"Sorry to wake you up. Sand annoyed Thorn and was sent to torturers and I ordered him to act exactly as if he were obeying their orders except while simultaneously minimising risk with the same phrasing we used before, and I also ordered him to go fetch more surveillance stuff while still minimising risk after it in case the stuff was destroyed but it turns out to have been unnecessary so I rescinded that order, and I thought you'd want to be informed of this and could potentially have something to say about it."
"If Sand were higher-up I'd think it might be but it's not a real risk with him, I think."
"Thorn's smart enough to think of it. But not everyone would have it."
"Mmhm. And hopefully the 'minimise risk of discovery' order would cause very uninformative grunts. 'All's clear.' 'Nothing weird tonight.' 'Everything cool.'"
And of course, under Mortal's anger and resolution there's—simple fear. Because. His mother is being tortured by this person. He needs to take him down. Is it so hard for him to just walk into his room alone?
Well, presumably Eveningstar was a nonsorcerous one, Sand is, too, and there were the others Verve mentioned... What does Promise think?
"There are some people who genuinely aren't sorcerers but there are probably also some who know sorcery and aren't allowed to use it, outside extreme circumstances or when expressly permitted or something. We don't actually know if Eveningstar or Sand can cast, just that they don't."