She spends a moment trying to gauge if this is a response to 'yes, he did hear me' or 'that did something else weird and bad'.

It seems like probably he heard her and this is just a very reasonable response to suddenly hearing a voice in your head, when you're already trapped in a pit next to blue goo which is eating you. 

:Please try to remain calm: she says. :I'm not one of the scientists from the experiment. We want to help you but I need you to stay calm and not make it obvious to them that I'm talking to you: 

He curls up on the ground and shivers and buries his face in his knees.

:It's okay. It's going to be okay. I know this is awful. But we're coming and we're going to - get you out, somehow: 

(She is super not in a position of authority to promise that, on strategic grounds or in terms of whether it's literally possible.) 

:My name is Emril. What's your name? ...Er, you can think it loudly at me and that should work: 

She's trying to read his surface thoughts already but he's very panicky and it's not especially coherent.

Fortunately it seems like the scientists are incredibly distracted and probably aren't watching their live human experimental subject that closely, and also his behaviour is pretty reasonable given the situation, telepathic voice in his head or not. 

His surface thoughts are mostly 'aaah'.

Are you my guardian angel? he thinks at her after a moment.

Emril has no idea what that means. It's a very weird concept. 

:No, I'm just a person. I'm a - doctor, you could say:

She...briefly considers telling him that she consented to letting the protomolecule infect her so that they could try to save his life, and quickly decides this is a terrible idea. 

:The scientists doing this to you are monsters. But - no thanks to them - I think you're going to be okay. The thing they injected you with is called the protomolecule. It's - an alien. It's very powerful and very confused and they're studying it and have no idea what they're doing. But I - we - have more of an idea, all right? And I'm going to show it how to take good care of you: 

That seems kind of ominous. Does it mean he will have the alien's babies. He does not want that.

:I'm pretty sure you aren't going to have the alien's babies!:

Telling them that she doesn't know what will happen, that they're figuring this out as they go, is probably not actually helpful, so instead she just pushes across nonverbal reassurance, and waits, while the Proto swims in her own blood as well. 

Leareth, after several minutes of failed multitasking, eventually thinks to call in one of the other Healers with Mindspeech, and delegate to them the task of snooping on the scientists' thoughts via Proto relay.

He's suddenly very tired. 

:...The Proto mastered Healing-Gift: he says to Julie and Nayoki. :I - think this increases the odds that we will survive:

A pause. 

:I think I want to give it Farsight too, if we can. Possibly Fetching although this has obvious downside risks. It will help immensely if we decide to rescue their human test subject, which my Healer seems to have just promised him we will try. Nayoki, please feel out whether we have a...volunteer, for that: 

"Are we headed to Ceres or Io?" he asks when the weird invaders surface from whatever it is they're doing.

:Io. Although it is not clear exactly what will happen there. Leareth - decided to open communications with the scientists at the research lab and claim to be from a different research lab in this star system, he is hoping to talk them out of the Eros plan by that route. And we do still need to transmit a message to Ceres as we go past: 

"I see," he says. "Sounds like a plan." It does NOT sound like a plan, or at minimum it sounds like a terrible one. He goes to find his crew.

Nayoki can get why Leareth at least wants to try this way before they go down the route of blowing up the lab from space, and he is putting a reasonable amount of care into not letting the lab team suspect that he is, right now, on a ship headed their way for exactly that purpose - but she's still uncharitably irritated with him for leaving her with the job of explaining his inexplicable-seeming decisions to this crew.

Who, to be fair, she's starting to find pretty grating. 

:Leareth thinks that we should hide our drive signature as we approach: she adds. :He has more ideas for ways to do this with magic, and we should have time to figure it out:

Separately, after a brief rest, Leareth reaches out with Mindspeech. Hunts around for Holden's mind. 

:This is Leareth. I want to speak with you at some point when it is a good time. Privately. I...am confused and wish to better understand some elements of this situation, and of what happened before we arrived: 

"Yeah, we should talk. Is telepathy not private by default? I can come down to the medbay, I guess."

:My half of it will be private by default. Though it might be more straightforward to have a conversation where you can actually see me and I am not just a disembodied voice: 

"Sure, I'll come down."

He does this. Puts on his respirator and crosses his arms. "Flip and burn for Io's in twelve hours and honesty, we're not at all persuaded that your plan here is worth enabling."

Sigh. :The plan where I try to convince the scientists that the ruthlessness of sacrificing a million lives is not actually necessary to further any of their aims? I - agree that they are unscrupulous but I do not think they were in fact planning to do this for fun: 

"The, uh, plan where we make the alien parasite stronger and teach it to be psychic and infect people with it. Stopping the mad scientists I am all in favor of."

This isn't the main conversation Leareth wanted to have but...it does seem like an important and overdue one.

:I think I have not done a very good job of conveying my context and reasons for wanting to do this. If you allow me to explain, and you still think I am obviously wrong, then I would be interested in hearing your case for why: 

"...okay, let's hear it."

:- It would be helpful, for that, if you are at the point of believing that I am really from another world and that we have vastly different capabilities than those that your civilization possesses. Are you?: 

"...I'll entertain it? I don't have a different explanation. But - other worlds shouldn't have humans on them."

:Trust me, I am just as confused on that aspect as you are!:

He closes his eyes. He's managed, through some sort of mindreading-osmosis more than anything direct, to pick up that starting with 'and our world has gods' isn't going to go well. 

:Velgarth is - in most ways, far less advanced than your civilization. We do not have space travel; we do not have electricity or computers; our total world population is less than a hundred million, and I cannot even tell you how much less because the planet lacks anything close to a centralized government, or the infrastructure to run that kind of accurate census. However. We - do have entities that are...somewhat like the Proto, in a way. Far more powerful than humans, superintelligent in some ways, but deeply alien and nearly impossible to communicate with. I am not sure where they come from. Perhaps they were built by a more advanced civilization, as the Proto was. I am not sure it matters at this point: 

How is Holden taking this so far? 

Well, given there are some aliens, there might as well be lots of aliens, sure.  And there being lots of aliens is also sort of the beginning of an explanation for the other world having humans. "Uh, if you don't have computers you might not know this, but did humans evolve on your planet? Are there transitional fossils, closely related apes?"

:Unclear. We might not know if there were. There was - a very destructive event, the Cataclysm, a few thousand years ago, that could have erased much of that evidence:

Making sense of the mystery where Velgarth and Earth both have humans is fascinating, but not Leareth's top priority right now. 

:Anyway. Our resident alien superintelligences do not eat things - they exist outside of ordinary three-dimensional space - but they do influence our world. Steer events. After the last few thousand years of our history, it is fairly obvious they are steering away from technological progress. Which, as I expect you know from your own world's history, means that Velgarth contains a great deal of pointless starvation, disease, and suffering. I - have made it my life's work to study these entities and attempt to communicate with them, in hopes of changing this: 

He hesitates, looking at Holden, trying to find exactly the right words.

:- So, I think I am the closest the world has to an expert in communicating with aliens. That is where I am coming from, when I say that the Proto is possible to cooperate with. It wants to talk to us. It is eager to follow any instructions it understands: 

(It likes math. It - takes pride, or something like it, in solving problems and building things...)