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—
"What are we gonna do, once they're all neutralised? Go visit and start interviewing vassals? Are we gonna move his court anywhere?"
"Interview vassals, see what they want to do with themselves - maybe use the sites for anybody who actually wants to live all together one way or another."
"I kinda have a sort of instinctive aversion to living anywhere the Queen could reach but I suppose it's pretty normal for most fairies. My brain is going all 'get this over with and run as far away as you can.'"
"You wound me. Have all these months together not given you an inkling about what kind of person I am?"
"It'll hold, I'm pretty sure. I never had a momentous thing like a promise to myself like you did, but... Something close enough."
"I'm... not sure. I don't know what-all is wrong, I might... get her a therapist, or something, and be there for her."
"...yeah. They might try to treat something she does not have because of the fairies thing."
"It could... get very, very bad. Depending. If they focus on the supposed delusions they might not treat the underlying problem, they might think she needs to be committed to an institution for her own safety, if I ask them not to try to fix the fairy delusion they might think I'm an unfit guardian and take her away..."
"Yeah, it's not. I don't know, I might show them fairyland except that would open its own can of worms and I'm not ready to make fairyland public like that."
"I'll... figure it out. Somehow. It may not necessarily be that bad, she could eventually cope, maybe."
"Yeah. They do. I don't... I'd expected something else. I'm not sure if she didn't recognise me or, or what."
"Yeah, I know, but..." He shakes his head, rubs his eyes, then opens them. "Speculation. I'll figure it out when I see her. No point worrying about it now."
The gate settles around when Thorn's approaching the last court.
And Mortal's mother steps through it and looks around, then at him, a bit blankly. She tilts her head.
"Mum?" he asks, taking a few steps towards her. "It's—it's me. It's Sadde, we got you." He looks over his shoulder, then at her again. "This is Promise, she helped."