As you leave the Main Hall, a white horse comes to you and seems to nod in your direction. As you draw close to it you hear it say, "My master desires your services, come with me," and beckons for you to climb up.
The horse takes you for some distance to the south before stopping at a group of bushes, just in front of a large cave. As you get down from the horse, you wait for about a minute.
Then, as you stand there, you see the knight marshal come out from behind one bush. You can see from his clothing that he's been in some sort of fight. He looks you up and down and then says, "Great evil has infested one of Eamon's best caverns. I was too late in getting people to help destroy the evil, but I see" (and he looks at you) "that at least one person might be able to help me. I will even come along if you agree to help."
Seeing that you have agreed, the marshal goes back to his bush, gets his gear and stands ready.