Sacred 2:An Eye for an Eye
Talk to the Fisher's Wife (widow really) to learn that she recognises the dagger.
Take the dagger to the guardsman! I... I know this dagger. It belongs to our neighbor! I don't believe this! Did he really...? Please make sure that justice is done. Take this dagger to the guardsman at the port and tell him about the incident. It will not bring my huband back but at least teh murder will not get away with it!
Murder? You are talking murder? That is a serious accusation. Well, now that you come to mention it... I saw someone run towards the tavern not so long ago. He seemed very agitated and obviously tried to avoid me. Still, as you can see we have by far not enough guardsmen around here. I cannot leave my post. You can take care of it - I have faith in you!
Head east and go into the tavern and talk to the inconspicuously-named ‘Murderer’...
What? Who? Leave me alone or else!
Kill him when he becomes hostile, then report back to the Guardsman for your reward.
Thank for taking care of that matter! Here, this is for you.