In the Dark Brotherhood quest The Assassinated Man, where you fake the death of Francois Motierre, you must enter the Chorrol Chapel Undercroft to revive him using the Langorwine Antidote. However, for me, the Chorrol Chapel Undercroft is locked and I need a key to open it. Does anyone know where I can find this key? I have KOTN if that helps, thank you in advance!