Why can't I see any other characters in "For the Alliance" in Undercity?

I have a level 80 Death Knight (Dranei) and want to complete the "For the Alliance" to get my war bear, but when I get there, all the other players disappear. I can see thier "dots" on my minimap, however. I'm told I have to complete the Undercity quest line in order to get into Undercity and Scarlet Monastery. Where do these quests begin?