My Quest Giver Just Became a Zombie?

I am playing Skyrim Dragonborn and I got a quest from Glover Mallory (who happens to be Delvin's brother) to find the Ancient Nord Pickaxe. Last known location was with Crescius Caerellius. Tracked this guy down, convinced Crescius to hand over the pickaxe before starting the mission.

Now when I try to return it, this is what I see. This guy is praying or proselytizing to an Altar?

The person Glover Mallory is like a zombie. WTF gives? How do I complete this quest?

A word no spoilers please. I still do not know WTF is happening. Thanks.

Solution 1:

Just continue about your business for now. You will eventually get (if you have not already) a quest that involves you breaking the enchantment that has taken over Mallory and others. When that's done, you should be able to wrap up his side-quest.

Note: I could go into more detail, and provide Wikia links, but that would be violating your request for avoiding spoilers.