Whispers in the Dark

Conspiracy
Astrid tells you about a matter she’s beginning to be worry about. Cicero is acting erratically, locking himself in the Night Mothers chamber. Astrid fears that he and someone else may be plotting some sort of a conspiracy. She wants you to hide in the Night Mother's Coffin and find out who he is conversing with.

Night Mothers Coffin
Upon entering the Night Mothers coffin, you will hear Cicero enter into a conversation with the Night Mother. Then Night Mother begins to glow. She will then tell to you how “You’re the one”.

Defiler
"Defiler," Cicero cries out when he find's you in the coffin, however when you tell him about how the Night Mother talked to you, he goes from being angry to dancing around the room.

Tell Astrid that the night mother wants you to find a man Amaund Motierre in Volunruud.

Bugs

 * A bug occurs after the coffin scene where you are told to speak to Nazir to find more contacts and there will be no option. Preventing you to continue the Dark Brotherhood quest line. To fix this open the console and type "SetStage DBSideContract04 0". This will finish the quest and allows you to take the contracts.
 * There is a bug in which, upon entering the coffin, Cicero doesn't say anything; you cannot leave the coffin. Waiting may work, but not always.
 * Solution: Entering the Night Mothers Coffin, then Waiting for an hour or two sometimes fixes the glitch.
 * closing the door to the room containing the coffin may cause Cicero to not speak after humming a little bit. this can be fixed by loading the last save and leaving the door open.