Noah looking for Nail with spirit sight and not seeing him I assume.
In retrospect, "You focus on the other flank, they need the help" from hoh_2179 would fit the famous last words... How would they deal with Chernyl without Nail though?
for the secret police his death would mean instant mission abort and back to the nuke "solution".

@Zyzyzyryxy It was established back in the Malhart chapter that Nail is invisible to spirit sight (to an extreme degree). I would expect Noah to be used to not being able to track him by now.

Nail is invisible to spirit sight, isn't he? Even Malhart couldn't find him.

@Baprr
Nail has no spirit as he isn't a magic user. What's interesting is that he also apparently doesn't have life signs

@Brilliand thanks, I forgot about that.

Noah can see Nail while in his spirit mode, as evident when he was following the green cat and saw Nail feeding one of the malhart kids medicine, and the cat hissed at him. It's more notable that Malhart could detect regular magicless life signs and not Nail.

Don't mind me, just adding to my previous point...
Magic sight is like normal sight but replacing light sources with magic sources. In both cases, it should be pretty hard to see non-magic users past a wall, as Malhart did (https://neorice.com/hoh_1980), rather he likely used a different spirit ability to detect life signs (https://neorice.com/hoh_1982)

Don't mind me, just adding to what I added.

What the hell is Nail, anyways? He doesn't bleed?!
https://neorice.com/hoh_noah_286

@TheMegax
Good memory!
Perhaps he's a construct, it would explain the lack of blood and some anti-Spirit shenanigans. (Hard to detect something that has absolutely zero spirit.)
That does raise a fair few other questions of course, and doesn't solve how he plans to definitively end the current crisis, unless it's just using black crystal weaponry.

@Charter
Either a (non-biological, non-spirit) construct, or a non-spirit based undead. No idea how either would work, of course.