private
Female death spirits. Drawn to old battlefields. They not just slippery, but blood thirsty, and have a grudge against the living.
Yeah, we've all put in a lot of research time by this point. Most leads are exhausted. I think it's time to ask him if he wants to go through with something like that. If he says yes and you can get those photos, they might offer you a focal point while we try to summon them.
Summoning the dead might be the only and best way to have first contact them, without sending psychic waves to another dimension. We don't know who - or what - might sense it from Point A to Point B. Then they might want to check out where it came from, and that's going to lead them to you.