Oblivion - Dark Brotherhood Quest 3 - Accidents Happen

The mini-quest to get the next contract from Valtieri is called "Blood of the Damned." Talk to Vicente to complete the mini-quest and learn that your new task is to go to the northern town of Bruma and slay a Wood Elf named Baenlin. It needs to look like an accident if you wish to receive a bonus reward. For the more direct Dark Brothers, sneaking into Baenlin's house and killing him and his manservant Gromm is very easy. However, doing so forfeits the bonus.
Vicente tells you that Baenlin likes to sit in his most comfortable chair every day between 8:00 p.m. and 11:00 p.m. It just so happens that this chair sits right under a heavy mounted head of a Minotaur. The head is loosely attached to the wall by a set of ropes which you can reach via a crawlspace. The crawlspace is accessed from the bedroom at the south end of the house's second floor; the door is in the southeast corner next to the desk.
Travel to Bruma. Baenlin lives in a house just north of the Eastern Gate. Enter through the basement door at the rear of the house for remotely safe and indirect access. Sneak upstairs into the crawlspace and wait till it is sometime between 8:00pm and 11:00pm. Make sure Baenlin doesn't see you, as he will leave the chair, at which point you have to leave, wait, and try again. It is possible to wait in the room above the chair if you close the door behind you. The game no longer considers you as a trespasser. Once you're in position, loosen the planks and the head will crash to the floor, killing Baenlin in the process.
Sneak out the same way you came and return to Valtieri in Cheydinhal for a level dependent gold reward (up to 600 gold), advancement to Slayer and, if you were worthy, the bonusSufferthorn dagger. If Gromm survives, you can find him in Olav's Tap and Tack, weeping over his dead employer. Baenlin's house is now occupied by the killable nephew Caenlin, who was most likely the Brotherhood's client for the accident.