This was a quest introduced for The Scourge Invasion world event in patch 1.11. The event introduces Naxxramas, a floating necropolis & home to the lich Kel'thuzad. The quests introduced for the event are no longer available.

i just got this quest today.. there isnt a follow up quest as far as i can tell yet..

How tragic. These words, clearly meant for someone the soldier loved, never made it to their destination. The events detailed happened years ago; I'm not sure if the intended recipient still lives.

There is hope yet, however. With the names and information he gives, I might be able to locate the family! It will take some research, but the librarian in Stormwind owes me a favor...

Thank you for bringing this to me. With your help we may be able to grant someone peace of mind at last.And confirmed at the moment - the Keeper does not offer a follow up to this quest.

Edited in for more information: This quest is also being 'reused' for the pre-launch events leading up to Wrath of the Lich King. I received this document from a Skeletal Soldier spawned by a Necrotic Shard in Tanaris.

This quest doesn't seem to have a follow up to it, even though the Keeper of the rolls mails you a letter telling you that the fallen solider has a sister in booty bay and asks you too give her closeure if you are ever passing through, but she is a vendor and all you can do is buy/sell and repair from her. So don't waste your time like I did finding her it is not worth it and you can't even talk to her to follow up the story line.

Just to clarify: this quest or any of the other quests started by quest items off the invasion mobs don't count towards the Loremaster of Eastern Kingdoms achievement. But if you're going to be in Light's Hope Chapel anyway might as well turn it in.