Guild Wars 2 – Discovering Darkness

Head over to the entrance of the Instance. Once inside you will find Caithe waiting for you on the other side.
Caithe: “The Nightmare Court is gathering. We must proceed with caution. I cannot approach them. They know who I am, so I'll watch from a distance.”
Hero: “I don't understand why we allow them to gather at all if they seek to corrupt everything.”
Caithe: “On those rare occasion when they bloom in public, they vanish just as quickly when the Wardens arrive.”
Hero: “If we can't approach them, how will we free the White Stag before they corrupt it?”
Caithe; “I cannot, but you can. You're a newly awakened sapling. They'll be eager to recruit you. Speak with them cautiously and earn their trust.”
Hero: “I will. Perhaps I can persuade a recruiter to follow me back here. Then, together we can force the recruiter to tell us about Gavin and the Stag.”
Caithe: “Excellent. Before you go, a warning, do not listen to their lies. If you become corrupted, there is no cure.”

After that conversation, head to the North through the trees to the clearing below. Just listen to their conversation. They talk of Ventari and Ronan and how they did not understand what it is to be Sylvari. After the speech the Recruiters will head a little ways off. Follow them. Talk with them and use your preferred personal interaction. There are 3 Recruiters. The female responds well to charm, the male by the tree can simply be convinced (as well as the dignity response) and the final one will take the bait for a fight.

Now head back up the slope to the South to bring the recruiter back to Caithe. She does not take well to being set up. She is a lvl 6 necromancer. Be on guard for the numerous status effects she can through at you. She will also summon a pack of 3 Nightmare Hounds.

After the fight it is time for some more conversation:
Hero: Listen here. You're smart enough to know you're in trouble. Tell us where you're keeping the white stag and you can go back to your friends.”
Recruiter: “If I tell you the others will hunt me down and make me suffer.”
Caithe: “Tell us where the stag is, or I'll carve out your tongue with my blade.”
Hero: “No, listen. Trust me. No one needs to know it was you. I won't betray your trust as long as you tell us the location of the White Stag.”
Recruiter: “I believe you. It's Gavin He has the stag caged in a camp farther north. It's a creature of hope, so turning it to despair will help liberate us – and the Pale Tree too.”
Caithe: “Thank you. Now, we'll keep our word. We won't tell anyone you talked … before you died.”
Hero: “Caithe, please. We're better served letting her go. I gave my word that we would. We're better than she is. Our word is our honor.”

it is at this point the mission breaks into one of 2 choices. You can approach rescuing the stag through Disguise (Hidden in Darkness) or deception (Saving the Stag). The choice is yours.