Board Thread:Skyrim/@comment-11982931-20130923051752/@comment-7953253-20130923070432

If the quest is glitched:

Sometimes, the muder may take a long time to occur and Susanna the Wicked will stay alive and continue working in the Candlehearth Hall. Or it may just take a while for the mission to trigger on it's own. (The appearance of the bloodied body at the cemetery)

Another approach is to break into Hjerim prior to starting the mission itself, by pickpocketing the key from Tova Shatter-Shield. Hjerim cannot be pick locked without starting the mission, only unlocked by key. Anyway, after breaking in and entering Hjerim, it SHOULD start the mission and skip the first few parts of the mission, but it's no guaranteee. Sometimes, even after entering the house, the quest will not proceed to the next part.

Your best bet is to just wait until Susanna's body appears.