Ahdarji's Heirloom

Walkthrough
You must get a ring back to Ahdarji that was stolen by an Argonian named Amusei. If this name sounds familiar, it's because he was the Argonian competing against the player and Methredhel in the first Thieve's Guild Quest. Do the normal Beggar Bribes to get the information, and find out that he is in jail. Go to the palace and then bribe the guard to go see Amusei. Follow the guard to the prison door where he will open it then leave then talk to Amusei and offer him a lockpick to escape. He will tell you that he saw that it said Alessia on it, so he tried to sell it back to Alessia Caro, and that you'll need to get it back. Again, go do the Beggar Bribes, and find out that you need to talk to her handmaiden, Hlidara Mothril. You could also get the jailer's disposition high enough and he will tell you, which is quicker than running after the Beggars. She'll tell you that she only takes the ring off when she is sleeping, and on the Ides of the month, she is gone, so the 14th through the 17th are off-time. Optional: Return to Ahdarji at that point and tell her about how Amusei tried to sell the ring back to Alessia. This will cause her to double the reward money. Alternatively, tell Ahdarji about it with the ring in your possession, just before returning the ring, to avoid running around needlessly.

Go into the castle basement following the marker, and on the South wall of the basement, there is an open barrel with a lever. Pull it to reveal a hidden doorway that leads to her majesty's torture chamber. Keep going upstairs, and you'll be right next to her room. Be careful, there is a guard patrolling the hallway in front of her bedroom. Keep following the marker, and go next to her bed where the Jewelry box is. Pick the Hard (Average for lower levels) lock and grab the ring. Make sure she is in bed and sleeping, otherwise it won't be there.

Alternatively, you may try and pickpocket her while she sleeps for the key, however, this may or may not work.

On your way in or out, it pays to explore other rooms. Some characters have gold and keys worth pilfering.

Take the ring back to Ahdarji, and then go back to S'krivva in Bravil to finish it up.

Bugs
In some versions of the game Alessia Caro might be sleeping but she doesn't put the ring in the box. If on the PC, one possible way to finish is by opening the console by pressing tilde (~) and typing in "player.AddItem 00035E95 1" without the quotes.

Another possible fix is to leave the castle, wait for 24 hours, and then re-enter.

Two Rings
If you find two rings, only pick up one of them and nothing else. Alternatively, you load the game and there should only be one ring this time. If you were to pick up both rings, you will only be able to complete the quest by using the console. Open it and type player.removeitem 00035E95 1.

Hlidara Mothril Dead
It is possible, especially if your character's level is fairly high (around 20 or higher), that Hlidara Mothril will be lying dead on the road somewhere between Bravil and Leyawiin. This is likely due to high level enemies roaming near roads, as Hlidara does not have a body guard, unlike the Countess. It is also possible that you will find her dead inside the castle, and, if you are early enough to see it, you will find she had been killed by castle guards. Fortunately, in most cases, you can skip talking to Hlidara, and simply head straight to the castle in Leyawiin to acquire the ring if the Countess is in town. It is also likely that if you attempt to revive Hlidara with the Staff of Worms, you will be unable to talk to her. If on pc, use the console code: resurrect 1 on her and she will stand up and come back to life.