[I haven't but I don't want to be in Leareth's head because he is sleeping with my brother.]

[What]

[Really?]

[Are they not different species?]

[Matirin gave Leareth morph after he was injured in an attempted coup by some Yeerks who disagreed with you about surrendering]

[Leareth goes around as an Andalite all the time]

[Huh] 

[Well, the Yeerk-host setup seems very good for research in general, so I think it is worth asking Leareth if he minds the morph very much.] 

[I will pass it along]

He does this, the next time he sees Leareth.

<It has not been one of my favourite morphs in the past, but Mhalir has a point that it will probably be more efficient for this kind of work, and I imagine he is very impatient to have his promised new body, so I do not mind trying it once. If you are comfortable having me in your head, that is.> 

<I don't object.>

Then Leareth can try morphing Yeerk and slipping in Cayaldwin's ear before they go look at his and Cayaldwin's work on this so far. 

Cayaldwin is such a wreck! He still has the random sores from not moving his body properly and the periodic dizziness and vision spotting that is probably from not sleeping or drinking enough and most of his head is a constant loop of 'everything important is gone forever' 'everything important is gone forever' and his thoughts frequently have to leap over enormous gulfs of things-he-doesn't-want-to-think-about.

He is self-aware about absolutely none of this and pulls up the computer. <Caught up?>

Aaaaaaaaaaaaah. 

<Give me one moment, please, I am orienting.> 

Bringing up the part where Cayaldwin is such a wreck is not going to be productive. Leareth deliberately stares at it for a moment, lets himself be very upset about it (thankfully Cayaldwin cannot read his thoughts right now), and then shifts his attention to the areas of Cayaldwin's mind that are actually about research. 

It's very unpleasant. But Cayaldwin coped better when he had Mhalir in his head frequently, before. And right now he can't have Mhalir, but Leareth can try his best to be a temporary substitute, catching their shared train of thought when Cayaldwin loses it to the constant loop, patch the gaps where he's leaping over forbidden thoughts, maybe nudge him to drink water occasionally.

And just talk to him constantly, of course, if only about the literal content of their research. He's so lonely. Leareth didn't even realize a person could be that lonely.

He's going to try this for one day and if Cayaldwin is less miserable at the end of it he'll say he doesn't mind doing it regularly, even if the remaining level of misery is a lot to deal with. 

Cayaldwin is somewhat less miserable while working; he can mostly focus his brain on it and it's interesting, even though it's not important since nothing will ever be important again. He will drink water when nudged, with only a minimal degree of grumbling.

And they can, in fact, make significantly faster progress this way, with Leareth doing his best to supply some metacognition for Cayaldwin without making it obvious that he's doing so. 

Probably Yeerks like being Yeerks and Mhalir enjoyed being in Cayaldwin's head, or at least found it unbothersome, for that reason? Leareth finds it draining. Also exhilarating in moments, though, when Cayaldwin is most absorbed in the work and they can fly through it at the speed of thought. He tells Cayaldwin that he's up for continuing with this until they've got actual-Mhalir his Yeerk body back, at which point he probably wants priority for being in Cayaldwin's head. 

Right, he can't exactly go back to Amanda. Maybe Cayaldwin can keep him full-time. He feels positively about this, insofar as he feels positively about things. And he shares Leareth's deep satisfaction when they're able to fly through the work. 

The format that information is kept in in z-space during morph is not the same as the format a backup is in, and it's not meant to be possible to interfere with, but Leareth has been interfering with it copiously when he does the nothlit-demorph, and Cayaldwin altered the morph failure state in the most recent version so it's easier to force a demorph with external energy. It seems like there is a similar set of changes needed here, to make a new form of morph which has the z-space pocket interpretable enough that the mind of the morphed rabbit-or-whatever-else can be replaced with a mind from a backup. The lucky thing is that if they fail repeatedly it's fine; it's not like they'll run out of copies of Mhalir, or like a failed copy will have any experiences.

He has to make a bunch of other changes to the morph setup for this to even seem possible but this setup doesn't need to be actually usable for more than the one 'demorph' back into a Yeerk body.

The most annoying thing about being in Yeerk morph most of the time is that he doesn't have Gifts. (Leareth spends a while trying to get a composite morph to work, but it seems like Yeerk brains, perhaps unsurprisingly, are laid out too differently to tack on human Gifts.) The upside is that Cayaldwin does have Gifts, and if he allows it then Leareth can bring across his own skill at using them, and this is actually very good for smoothly multitasking, doing magical work while also holding very complicated planar concepts in mind, because Leareth can do the former while Cayaldwin does the latter in literally the same brain. Incidentally Cayaldwin will rack up some amount of procedural memory for magic use, though not as efficiently as if he were really doing it all himself. 

It's harder to document their work and keep Mhalir up to speed this way, both because they go a lot faster and because they can more easily communicate in not-quite-verbal intuitions, but Leareth is also trying to make this both replicable for a Mhalir-and-Cayaldwin team later, and possible to write up clearly to share with other Andalite scientists, so he spends some time documenting it.

To the extent he can do so while minimally disrupting their work, Leareth nudges Cayaldwin to drink water and relax when he's holding his body tensely, and stretch or walk around sometimes. In response to any grumbling, he points out that if Cayaldwin is dizzy and sore then he has to experience this too. Leareth's morph time limit has enough leeway that he can sleep in Cayaldwin's head, and usually does, it means he can nudge him directly from work to joining the Andalite herd when he notices Cayaldwin is getting tired, and then talk to him - about research, but with the purpose of keeping him company - until he actually falls asleep. When he desperately wants time alone with Matirin in Andalite form, he usually does that in the mornings. 

Mhalir is lonely, sometimes, when Cayaldwin and Leareth are too wrapped up in thought to write out messages to him. But there's a lot of Internet to read to keep himself distracted, and he reminds himself that at least Cayaldwin isn't lonely like this. 

Cayaldwin is not paying any attention to anyone's stupid psychodrama about who is lonely and who isn't. His two moods are sadness and math and lately it's been more math which is good because math is more interesting. He drinks water and shifts his weight and mentally rolls his eyes about Yeerks being so finicky though it kind of makes sense that being unable to fidget a body would be annoying like an itch you can't scratch. He is happy to spend his time in morph with Gifts which Leareth is allowed to use, it does seem efficient and also if anyone were to attack them or something it's by far best for Leareth to have the Gifts.

He reformats and reformats and reformats Mhalir, trying to put together something that can be subtituted into a morph-construct. He makes suggestions for Leareth's paper on this topic; Matirin thinks it's best for Cayaldwin's name not to be on the paper, given Cayaldwin's known close relationship with Mhalir, but he can certainly look it over and improve it.

Nobody attacks them or something, to Leareth's relief. 

Leareth drafts and re-drafts his paper through several versions, fitting this in when he's not in Cayaldwin's head because Cayaldwin finds it the least interesting part of their work. Eventually he thinks it's ready to publish, and maybe they can get input from other Andalite scientists' commentary on it? 

The publication process involves paying researchers in the field to read and revise it; hiring the best people in a field for this is expensive, but Leareth is astonishingly rich by now, so it's not much of a barrier. 

The scientists are really intrigued! This seems like a really promising line of research and if it did work it'd be a big deal. Backed-up Andalites all have living wills specifying how experimental efforts to revive them are allowed to be, and some of them permit being test subjects for this. They invite Leareth to the homeworld for a collaboration.

Leareth would be delighted and honoured to travel to the Andalite homeworld for a collaboration! 

Presumably Cayaldwin should not come, given that they're trying to avoid associating his name with the project. Leareth is in practice less smart this way, with only his one brain, but there'll be other scientists to work with, and meanwhile Cayaldwin can keep working on the formatting issue with Mhalir. Also once they do have Mhalir back, he'll need to get used to having one person's worth of brain again. 

(He's a little worried that Cayaldwin will immediately go back to not drinking water or sleeping, but there's not that much he can do about it.) 

Cayaldwin does not consciously think that he will miss Leareth or in any way acknowledge it. He does think that his father would have liked Leareth a lot and they would have been very productive together, a thought which produces an intense flash of pain and makes him forget everything else he was working on; he avoids it after that.

So Leareth Gates across to the Andalite homeworld and travels to meet the scientists he'll be working with. 

Mhalir is on some level actually happy about this, he can go back to talking to Cayaldwin all the time. Except when he's off at night, which hopefully will continue serving as a prompt for Cayaldwin to SLEEP. 

Andalite research scientists are virtually all women, since all men have been being drafted for the last forty years. They've very pleased to meet him and excited in a restrained sort of way about ending death, on which the Andalite cultural consensus is apparently a comfortably uniform "it is bad". Also several of them think he's cute. Many of them worked on morph and can provide more insight than could be gleaned from the blueprints into what the morph-construct is doing; it's more complicated than just digitizing the mind, or this would be easy, but they think that the avenues of research mentioned in his paper are promising, and once the paper is published there'll be more people looking at it, probably. 

What a correct consensus for them to have on death.

It's really useful to have more insights on the morph process, and Leareth can show them his various ways of manipulating the morph pocket directly in z-space and then figure out more clearly what new capabilities he needs to add there, and what the other missing steps are. 

He doesn't know what to do about the part where several of them think he's cute, so he mostly ignores it. 

Having worked directly on morph means they think of a bunch of things he and Cayaldwin and Mhalir didn't. Demorphing into your original body is supposed to work differently than morphing a new body, because you want your physical brain to take up the cognition, you don't want it to keep happening in a pocket in z-space. But really if you think about it you could just consider this two different kinds of morph, rather than "demorphing" and "remorphing" - morph-into-a-brain-you-want-to-use, and morph-into-a-body-you-want-to-puppet. This might have some applications for embodying people from backups, which is a task where you want to put people back in their brain, so to speak.