Okay, got the quest to trigger (whee! )
Talked to witnesses, followed the blood trail, got the key, investigated the evidence and picked up the journal and strange amulet. I took the amulet to Calixto, like Jorleif said. He tells me what it is, and that it was Wuunferth's. My journal still says to follow up on the evidence, but quest marker no longer point's to Calixto's, and Jorleif has nothing to say. I cant find Wuunferth, he's not at the Palace of Kings, and didnt notice him around town unless I missed him somewhere. So what do I do next?

I'm on PC, in case I need to use the console to summon him up.

wuunferth's room is in the first door left when you enter the palace of windhelm

You need to talk to that lady that spreads rumors constantly. I can't quite remember her name.

Viola? No topics relating to the murders.

you also can pickpocket a key from calixto and find some evidence in a chest in his museum. but i'm not sure if this is needed to proceed

make sure you picked up some of Viola's flyers about the Butcher from Hjerim because I dont think her dialogue triggers unless you have at least one on you

Yeah, I'm playing the quest right now. Didnt have any fliers on me, and missed a second journal. Its advancing now. Thanks

Oh, so as an update.

I tracked down the murderer. He was attacking his next victim, despite 3 witnesses and a guard nearby. So I dash in to save her, and perform a double impale power attack, as the guard stands watching. Not so much as a thank you from the woman he was trying to kill.

lol. sounds about right. i think she may have even called me a 'nasty elf' when i rescued her.

Y'all are so lucky. This quest is permanantely bugged for me.