Windhelm - I ended up talking to the Helgird in the Hall of the Dead before instructed to by the quest. Now whenever I try to talk to her she only says, "Large cut from left shoulder" or something like that. I have three open items for this quest: talk to Helgird, search the crime scene, and ask Jorleif for advice. None of these seem to do anything. Is this quest unfinishable?

This is the buggiest quest in all of Skyrim. I go finally got my first bug. The guard never showed up. For you, I recommend reloading an earlier save.

Edit: follow the blood trail.

Yes, the quest is bugged. Horribly bugged. Famously bugged. To the point that its bug section on UESP was divided into four subsections.

Reloading a previous save is probably the best option.

This quest is so damned buggy, that I always take the shortcut to completing it. (Break into the house without talking to anyone.)

Took me forever just to be able to activate it. Very very very did i say very buggy

At that point in the quest: