I'm doing the Pieces of the Past quest line and Silus (the quest giver) is hostile to me. I was in the museum when a guard started to attack me and Silus joined in. I still got the prompt to meet him at Mehrunes Dagon's shrine. So I ran away from Silus, and traveled to the shrine only to find him still hostile.

You're going to need to reload an earlier save, methinks.

Kill it.

Back to another save.