"Good news, bad news," Micah says, clearly putting a brave face on things. It's a little of both. It would have been nice to find this lost Ghost in perfect condition, but at least they're alive.
The trouble is that it's difficult to know how to help. Simply exposing this Ghost to the Traveler's Light didn't seem to do anything immediately, but the Pale Heart is full of wonders. The line to Micah crackles as she hums in thought.
"Heal one, heal the other, maybe?" she says eventually. It's hard to miss that the Traveler's as hurt as this Ghost is, even if it's in a different way. The growth in the Arbor suggests you're on the right track, but not enough yet. Micah asks you to make a sweep around the Pale Heart, looking for things out of the ordinary—concentrations of Light that beg to be freed, or especially virulent servants of the Witness attacking vulnerable places.
It's just a hunch. But it's the best you've got, and this Ghost is counting on your help.