Was making my way from Riften to Dayspring Canyon. The Riften guards behaved as normal. Fought a couple bandits on the way. After that everyone became hostile. First an Imperial Courier, who just ran off. Then a random encounter Mercenary who relentlessly attacked me. and finally, the first NPC who talks to you when entering dayspring canyon the first time. Said his into line and half way through attacked me.

What should I do?

The best thing is to reload a game ave before they started to attack. Was there a dragon attack or something and did you hit someone with an aoe spell or something. I find usually the aoe spells are the ones that can get you wanted quite quickly.

Son, you've got a condition!

Sorry, love that line, and couldn't resist!

Any chance you contracted Vampirism during the bandit encounter? I think that makes people hostile toward you, doesn't it?