They send someone to get the reply from the drop site, once it arrives.

Leareth's letter says that he is willing to be read by a Thoughtsenser, but he wants to impose some conditions. He would like the Thoughtsenser in question to not be a Herald, not to have mage-gift, and to be someone who 'knows what they're doing' and can do a deep-scan without leaving a mess. He intends to have someone on his staff vet the Thoughtsenser selected beforehand, and he wants his people collect them and bring them north, alone, to a secure location, rather than Leareth himself coming out. He of course will promise them safe passage. 

Do the Heralds know some Thoughtsensers they'd vouch for (or at minimum be confident aren't working for Leareth already) who are not themselves Heralds.

Sandra thinks their best bet is probably a Healer with Thoughtsensing. She passes the message on to Savil so they can consider it; she's been trading off on the spell with Mardic and Donni, who are very good at concert work and add up to one full Adept when working together. For less urgent messages they've moved a Herald north of the border to complete a Mindspeech-relay, but this seems more on the urgent side. 

- speaking of communications, though, do the Andalites have any kind of artifact they can use to talk to each other? Sandra knows they can't give it to any Valdemarans, but if they can drop off an Andalite representative in Haven to be a communications person, she won't have to keep tiring herself out staying in communication and will be able to focus on defence here. 

The Andalites can send someone to Haven to be a communications person, sure. They can bring the recording of both Leareth's explanations under Truth Spell for Randi to review as well while they're at it. 

Shortly later, a conversation is taking place in the House of Healing in Haven. In Mindspeech, because Vanyel is currently asleep. 

:Yes, I know she's most qualified: Savil snaps, :but she's busy: 

:I'm sitting here watching him sleep: Melody points out. 

Savil's hands twist together in her lap. :What if he wakes up and needs you?: 

:Savil, hey. I know you feel out of your depth, with this, but - he needs you more than he needs me. I can't actually fix this by throwing blocks at it, especially not when half the problem is that he's exhausted: 

:I know you're worried about him. But you don't need to do anything other than be there when he wakes up and give him a hug. And it's not like this is going to take days. I'll come right back: 

:–What if you don't? This is Leareth we're talking about. What if he betrays us and murders you?: 

:What in all hells would he get from agreeing to be deep-scanned, vetting a Mindhealer, and then murdering them? He wants this alliance desperately. If he didn't want this alliance he wouldn't be bothering with any of this hassle: 

:You're not - concerned...?: 

:I'm scared shitless. However, this is my area of expertise and I'm the most qualified person in Valdemar to do it, so I'm volunteering anyway: 

...A few minutes later, a worried Herald Tantras brings Melody to the Andalite communications person. "We've got a Thoughtsenser to send up north." 

<Thank you. Are you ready to leave now?>

Melody takes a deep breath. "- Tran, remember, when he sends me back, have someone back at the ship check me for compulsions before you let me anywhere near Haven. And - then have Gemma read me, once I'm back here. She's known me since I was little and she's been in my head before, she'll notice if he messed with me." 

And she turns to the Andalite, chin raised. "Yes. Ready." 

The shuttle takes her north. 

<Will your Thoughtsenser take it badly, later, if we put a microphone on her now without informing her. I assume that if she is aware of it Leareth can learn it from her.>

:They're sending Melody?: Mardic knows Melody rather well. He's not going to mention that, given their entire reaction to Vanyel, which he's still kind of pissy about on poor Van's behalf. :No, she won't mind. She's very sensible: 

He nods. <Will you Fetch another one onto her when she arrives, then, please.>

Mardic can do that. 

Melody, when she arrives, seems quite calm and matter-of-fact about the whole thing. She's fidgety, but she's always fidgety. :All right, what's the plan here - you're going to drop me off somewhere and he'll collect me?: 

<We can leave a note at the drop point naming you and arranging a pickup assuming he's satisfied. How long should we expect you to be gone if all goes well?>