"Probably not fairies, then. Do you need me to make you any more harmonic maps or are you all set?"

"We can't test the intermediate versions without them. If you need us to leave you alone, by the time we return we'll have something that seems like it should work, but it will have been built blind."

The device is making progress. A few times one cape or the other will leave and come back with tools or parts; part of the huge room is turning into an impromptu workshop. When one of the attempts manages to make the harmonics within the room undetectably close to flat, they move the equipment closer to the door and keep working.

Promise can make finer-grained maps if they're getting that close. And three-dimensional maps.

Promise does eventually need to sleep.

Physical needs are inconvenient. But when she turns down their offer of advanced stimulants they are capable of acknowledging that decision. They'll be back the next day.

And Promise curls up on the bed she was supplied, with her bag under her arm and a ward around her and it both.

They leave a cell phone and instructions for whenever she wants to continue. They never did ask how much down time fairies prefer, and for that matter Armsmaster has more or less forgotten how much humans who aren't him do.

Well, Promise sleeps for about eight hours and then tests her gate and nibbles on her food and calls.

"This is Armsmaster. You're ready to resume?"

"Yes, whenever you like."

Fairylight!

It works as expected. Then Armsmaster touches a switch and the fairylight gets shredded. "That was the easy part. And outside?"

Fairylight. At least for longer than a few seconds. After a minute or so, "Can you try something more complicated?"

She attempts to turn invisible.

She disappears—not according to his vibration sensors, Armsmaster notes, though maybe she has something else for that—and a few minutes later the machine starts smoking. Promise reappears and the light stops.

"Is it supposed to smoke like that?"

"No. But it means the problem was with building it, not designing it. Should be easier to fix." As he and Dragon resume working on it, Armsmaster asks, "How does your translation work? I was almost expecting the phone call to come through as gibberish."

"I don't really know. I just talk, and people can understand me when I talk, and I can understand them, and it seems strange that mortals do it any other way. As though you've invented an elaborate code or something. But how it works I couldn't tell you."