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—
"So we order her right now to pretend to obey this kind of order in a way that won't bring attention to us, and then when we belay the order she'll revert to that?" he asks Promise.
"That's the idea. It's very timing-delicate but not as much as a longer sentence."
And if there are any loopholes in that...
"I'm kinda worried that she hasn't pointed out any loopholes yet and am not sure whether I should take that as meaning the orders are good or she's just doing her best not to think very hard of them right now."
"There we have it," he sighs to Promise. "In general, try to think of loopholes in my orders. Are there any in the orders I've given you so far?"
"Under your current orders, and assuming we find a way to prevent another fairy's order from taking, would you be able to use this distress signal?"
"Are there any more contingencies you know about or whose existence you suspect?"
"Can you think of any other questions about that or ought we move on?" he asks Promise.
"Next is names, particularly in the court you were going to. How's it set up, and whose names do you know?" Pause. "And by the way, what do you prefer to be called?"
"Mirror is the site coordinator and the place often has Rainfall there for major sorcery. Patch runs torture and Treecreeper helps, Mesmer runs the library, Harp and Songstress and Delight are midlevel incidentals, Awesome, Windy, Poplar, Deciduous, Eveningstar, Trance, Endpaper, Scribe, Enlightenment, and Sand are low-level post-project fairies permanently assigned to the site. Others of about my description may be there at any given time. I know names for Delight, Awesome, and Sand. I'm Verve."
He writes it down on a separate text file. "Tell me their names and describe me them in sufficient detail for me to recognise them if I see them."
He writes the names down but not the descriptions, because it'd be rude, but the conversation is being recorded anyway so that's more-or-less moot. "What can you tell me about the security procedures?"