It seems you have to specifically use the blood stone that you find in Maradino's hidden room.

I had to drop the other blood stones I had in my inventory on the ground, then talked to him about blood stones which gave me Frederick's Blood Stone quest.

Then I retrieved the one in Maradino's room, healed him with it, and was able to finish the quest without him trying to kill me

See my next post

Last edited by HauntedPast; 07/07/14 02:39 PM.