Now what could be happening here hmm? 
Before you ask Arn can tell something is amiss with Eilis, but he can't see what she sees. He just feels her energy is disturbed.
But the battlefield will demand your time as you fly into the warzone again, so questions later...provided that we all make it. 
(And no that is not a joke, now don't fret about right or wrong ways to go at this, all I am saying is like a real war the stakes are high.)