The Coldest Sleep
Yet another mission just like the previous ones. This time your victim is Havilstein Hoar-Blood, hiding in a camp at Gnoll Mountain. This time it's not complicated, as you don't have any other possibilities rather than killing him in a traditional fight. Your reward is in an underwater chest in Ayleid ruins of Nornal (you'll have to lockpick a door underwater).
A Kiss Before Dying
Go to Bravil and sneak to the Old Lucky Lady statue. About 6 A.M. and about 1 P.M. and elf named Ungolim comes here to pray. Sneak on him and kill him. This time the city guard won't interfere. After you get rid of Ungolim, Lucien appears and asks you just what the bloody hell you are doing. It turns out that your missions have been faked, and you have just eliminated most of the Black Hand itself!
Following a Lead
Go to the place indicated on your map as a next dead-drop location, next to the barrel behind the statue in Anvil. Soon, an elf named Enilrorth will appear. Talk to him to know that he's only been hired to deliver this message. He tells you that the traitor is living in Anvil Lighthouse. Go to the top of the structure and talk to Ulfgar the janitor. Frighten him a bit and he'll give you the key to the basement.
Go through the grotesquely decorated room and approach the 'shrine'. Take the traitor's journal and the mother's head. Head to Applewatch - the place where you killed Draconis' mother.
It turns out you're too late. The rest of The Black Hand have already taken care of Lachance, who was accused of treason. You are to take his place as the Speaker. Wait until midnight and talk to the elf Arqueen, then agree to go with the rest to consult the Night Mother.
HINT: You can use the Mother's Head in here in Applewatch. Just drop it on the ground in front of the whole council. The traitor will react to it, but you can't expose him yet.
Honor Thy Mother
After a short cutscene, join the rest and enter the crypt. The traitor will strike now, killing some Black Hand members at once, and trying to assassinate The Night Mother herself. Get rid of him, working together with Arqueen. When he's dead, Mother will promote you to the rank of Listener, and allow you to take anything you like from the crypt (some random items, quite good indeed). Talk to her once more and you'll be teleported back to the Sanctuary in Cheydinhal. Now to start your new life as a Listener.
As the Dark Brotherhood's leader, you have but one task to perform: each week go to the Lucky Old Lady statue in Bravil and listen to what she says. Then pay Arqueen a visit and deliver Mother's words. You'll get some gold each time you do that.
Besides, when the Sanctuary starts to fill with new recruits, you'll be able to tell one of them to follow you around. You can call it a free bodyguard.