Go to Solitude and head to the Blue Palace . Once inside, locate and speak to the Steward, Falk Firebeard . Ask him about Wolfskull Cave and after talking to him this quest will start.
Leave the Blue Palace and fast travel to the closest place if possible (either Ironback Hideout or the Statue to Meridia) and proceed to the cave. There are some skeletons outside, so take care of them before going inside.
Once inside; you'll find a lone patrolling Draugr Restless in the second room, so sneak attack it. From here, you can go either down the path or across the upper grassy one. Follow the upper path and you'll find two Necromancers around a campfire.
With your bow, you'll be able to kill them without them noticing where you are. There's a chance another Necromancer and a Draugr Scourge will come out of the door nearby. Take them out the same way. In the room behind the door, drop down the hole and proceed to the Wolfskull Ruins.
In here, you'll see some type of ghostly aura gathering. Looks awesome! Go left and you'll find a Necromancer. Kill them and proceed to the main room, where a Necromancer and a Draugr Scourge await.
Enter the tower-like building and when you reach the top, look for a lantern and shoot it down to kill the Draugr there. Go outside and there'll be a Draugr Deathlord and a Necromancer on top of the stairs.
Kill them with sneaky bow attacks and proceed. On top of the second set of stairs, you'll find another Draugr and a Necromancer. Kill them both and proceed to the next tower, where you'll find 2 Necromancers inside and on top, 2 more Necromancers PLUS the Ritual Master. Rather easy IMO. Be SURE to check the main altar for the LIGHT ARMOR SKILLBOOK 'The Refugees' . Lower the bridge and cross it to find a chest with your loot.
Now simply leave the cave, return to the Blue Palace and speak to Falk Firebeard. Tell him you stopped the ritual to be rewarded with some gold and to finish the quest.
Note: After some time has passed (it happened after I leveled up, so that may be the trigger), you will get a courier giving you a letter from Falk Firebeard to come see you again. This will start the quest " The Wolf Queen Awakened ".