When you get back, talk to Vilkas who will explain what’s been going on while you were gone. He’ll talk you into joining him for some revenge. He will tell you that you’re headed to Driftshade Refuge, the Silver Hand’s main headquarters. When you get there, make sure you watch out for guards posted outside.
Once you get inside, you’ll be greeted by the Silver Hand. Kill the few guards in this first room. Go down the stairs in front of you and take a left. Go through the door and walk to the next room. Follow the left wall to find a doorway just beyond the bookshelf. Go down this hall and open the door at the end.
You’ll come to a room with two floors and an enemy to your left. Kill him and then head downstairs. You’ll likely meet another Silver Hand on your way down the stairs. Kill him and go through the only door in the room. This will lead you to a dining area with a couple more Silver Hand. The one sitting to your right usually turns out to be an archer so you may want to deal with them first. If you check the side room, you’ll find lots of food and ingredients.
To open the gate and get out of this room, you’ll need to activate the lever just to the right side of it. Go through the gate and open the doors at the foot of the stairs. On the other side of the door will be a hallway. If you go up the hallway a little and do a u-turn at the first turn, you’ll find a little alcove with a chest and dresser. Turn back around and continue in the direction you were going. When you get closer to the end of this hallway, you’ll see some light, a pressure plate on the floor, a swinging spike trap and likely a Silver Hand attacking from the left. Let him come to you and have him run over the pressure plate. If he’s still alive, kill him. Do another u-turn to the left here to find another alcove/chest.
Turn around and at the intersection, take a left. Follow the hallway until you go through a wooden door. You’ll come to some kind of brewery and be attacked by a Silver Hand. Dispose of him and then head into the snowy cave.
In the snow caves, you’ll come to a medium sized, two level room complete with werewolf heads, a couple of cages and some Silver Hand. Kill the Silver Hand enemies in here which will have a variety of weapons. Once they are disposed of, you can set the werewolf free from his cage if you like but if you are not in your beast form, he will attack you.
Exit the room through the only other cave. You’ll leave the snow cave and come to a torture room with a single Silver Hand. Kill him and continue to the next room. You’ll start on a large balcony overlooking a fire and some chairs. There should only be two Silver Hand in here, one archer and one melee. Kill them. Take the tunnel off to the side and at the end, go through the wooden door.
On the other side of that door, pass through the tunnel and the room beyond. You’ll soon come to the final room where a group of aggressive melee warriors will be sitting at some tables on raised platforms.
Deal with the Silver Hand (which you should be an expert at by now). They are all melee and you have a companion with you so take it easy and slow. Once they are all done, grab the fragments of Wuuthrad from the table on the left and open the Boss Chest on the platform to the right. When you’ve taken your loot, head right up the middle and through the barred door to the exit. Leave Driftshade and return to Jorrvaskr for Kodlak’s funeral.