You need to find a hidden cove inside the cave in the forest. Calen will comment that he hears voices when you're near it. Listen to them talk repeatedly in the diamond hole until Drok'tar mentions he'll there's a good bakery in town. He'll show up in the bakery, talk to him until he'll mention he's going to the store for supplies. Drok'tar will then be in the merchant's store next door, talk to him again until he'll mention he's going to the tavern. Talk to him in the tavern. The next time you revisit the hidden cove in the cave, you'll see Drok'tar's scene.