Thane continues and then lets the silent bandit up, "Ready to talk now?" he says to him and if he gets no reply he waterboards him again until he talks. At some point he will ask the others why this one bandit is so silent.
The two bandits howl from the pain of Drethen cutting off their fingers. Once he lets them go at the cave entrance, they run down the trail towards the road without looking back.
As Thane is engrossed in his work, he doesn't notice the other two bandits are gone until he asks about the stubbornness of this one. That's when he looks up and realizes that Drethen has released them.
As for the bandit, he continues to give nothing but a defiant stare. And his reaction to Thane's treatment gives you the impression that he's been through this kind of thing before.
Thane says to Drethen, "What the hell? We weren't finished with them, plus what's the rush? They may now run to get reinforcements to help or did you really think they will now start to be saints?"
Thane looks back at the bandit who is not speaking then turns to Drethen, "Here, see if you can get him to talk." Thane leaves the room shaking his head. He goes towards the slope and starts his usual checks.
"So I figure you must be a bandit leader, keeping silent, hoping and praying for your friends to come to the rescue. Well as you can tell it is not going to happen. You really have very few options left. Information to give us is probably all you have left to sell us to save your life. My friends here are pretty ruthless and love chopping stuff up? Will you speak or die?"
Drethen come over to him and shows him the fingers of his comrades. "I guess it is your turn to lose a finger or two. Let me here you scream in pain", as he says this he cuts of the mans left little finger. "Now you have been marked as a thief too."
Thane investigates the sloping passage to the north. He finds that it comes to an intersection. To the north is a 10' alcove. To the east is a door and to the west is a passage.
In response to Drethen's comment, the bandit looks up at him with the water dripping from his face and responds, "There are worse things in this world, or these caves even, than you."
First, Thane will check that those corridors don't have anyone in them. If they are clear then he will investigate the door then open.
Out of Character: Those who aren't really doing anything with the interrogation feel free to backup Thane.
"Well then maybe you can help us out and be some bait." Drethen makes sure his hands are tied and then ties a rope around his waist and passing through between his wrists to make sure hands are secured down. The rope will have a five foot lead in back so the bandit can not go too far ahead. "Now lets go see what is so bad in this cave." Drethen pushes him in the direction that Thane went.