Arrow of Extrication
After you have completed the "Turn a Blind Eye" quest and fenced 700 gold worth of stuff, you'll get a journal update on the "Independent Thievery" quest telling you that the Gray Fox will probably come looking for you. This quest follows the same rules as before, except that the meeting is going to be in Chorral, so you will get no message there. Amusei is the messenger this time. He looks like he's doing quite well for himself. I guess that life in the Thieves Guild agrees with him. You're to meet with the Gray Fox at Malintus Ancrus' house in Chorral (it's one of the smaller houses down the road from the Chapel - just follow your compass marker). Ancrus will be waiting outside, so you should proceed inside and speak with the Gray Fox.
He would like for you to steal an item known as the "Arrow of Extrication" from Fathis Aren, the court wizard in Bravil. You can even kill Aren, if necessary, but please don't do it in Bravil. The Gray Fox wants this item pretty badly, it seems.
So off to Bravil you go. Any beggar with a disposition of 70 or better (or cough up 20 gold), will be able to tell you that Aren has a tower outside of town where he keeps his goodies, but that he is the only one who can get into it. You'll also learn of secret passages in the castle. Anyone else in the castle will probably be able to tell you that Aren has a room in the north wing of the castle and likes to hang out with Daedra (which is a good clue on what to expect on the way).
Getting to Aren's quarters in the castle is going to be a bit of a chore. You're going to have to open the locked door in the center of the balcony and there are always two guards standing by it unless the Count is in the Hall. Those with decent Alteration skills will be able to use an appropriate "Open" spell from a safe distance. Everyone else is going to have to sneak up and pick the lock right under their noses. Since this door is an area transition, you're going to be tresspassing as soon as you open it and the guards will undoubtedly take exception to this.
I've had decent success with Strong Chameleon potions combined with a good Sneak skill. Invisibility spells and potions go away as soon as you interact with anything (like the door or the lock). Whatever you choose to do, make sure that you save the game before doing anything where the guards might detect you and again when you're through the door. There are a couple of guards patrolling on the other side of the door, so a "Detect Life" will be very handy once you've made it into the north wing.
Once you're into the north wing, take the first left and pick the lock to get a message that you're in Aren's chambers. Unless you feel like looting the place, you won't find anything that you need in here. Opening both chests on the left wall will net you a message saying that the Arrow isn't here. But there is a secret door (activate the appropriate pillar) that will take you into the Wizard's Grotto and from there to the Wizard's Lair, which connects with Aren's tower. You'll find lots of leveled critters and a few Daedra and Conjurers guarding the passages.
These areas are full of twists and turns, but there is only one point where it's very easy to miss the correct path. In the Wizard's Grotto, you're going to have to swim across a flooded passageway that seems to have no floor (it does, but it's waaaay down there, along with a giant slaughterfish if you're in the mood for sushi). There is a submerged rock overhang on the left side of the passageway and you'll have to go under it to find the passage to the tower.
Once in the tower, you'll run into some Daedra. Getting to Aren near the top of the tower isn't a direct path because some of the floors have fallen out. You may find it easier to simply go to the top of the tower and then drop down through one of these breaks to get to Aren's room, but you might be able to pull it off with a good Acrobatics and Athletics skill.
Aren is standing with his back to the door, so it's not difficult to sneak by him and get the Arrow (it's actually a "key-shaped arrowhead") and the tower key from his chest. Members of the Mages Guild should take note - Aren is a member, too. Getting caught in this theft will get you expelled from the guild (20 Dragon's Tongue and 20 Redwort flowers for pennance if it's your first or second offense). And of course Aren will take exception to all of this (20 Daedra Hearts and 20 Vampire Dust for pennance if you actually kill him). Be careful.
Return to Ancrus' house to deliver the Arrow. The Gray Fox will give you 500 gold, promote you to Master Thief and give you access to the the last of the Guild fences: Fathis Ules, 1500 gold and 100 Mercantile.
Interestingly enough, aside from the Gray Fox's comments about future plans at the end of the quest, there is no new Gray Fox trivia in this mission that I've been able to uncover.