This mystery can be found in western Jorvik, beneath the northern bridge which links east Jorvik to west Jorvik.
When you approach the bridge you’ll hear a man crying out for help. Use Odin’s Sight or your raven to locate him beneath the bridge, then speak with him. He’ll tell you that he was accused of theft, and it seems he has paid for it by being blinded. Pick him up and carry him to the bridge by hopping over the wooden platforms to the north. When you reach the bridge a cutscene will play, during which the people who blinded the man will demand that you give him over. The scene will end with the man being taken away and the mystery will complete. However, if you want a good outcome for the man, you can kill the criminals and free him. He will then thank you can sit on the bridge.