When I was playing on my Redguard who sided with the Dawnguard, I was going to find the Moth Priest who could decipher the Elder Scroll. So I went in, killed the vampires, and Dexion spawned outside of the barrier thing (not sure if that is not normal, because I played with my other character who sided with the Volkihar vampires and he was inside the barrier). After I opened the barrier, he went crazy (as with the Vampire questline) and attacked me and Serana. I got him on the ground but there were no objectives completed or anything. I talked to him while he was on the ground and it continued as normal, but whenever he stood back up he would attack again.

Next, he said he would go to Fort Dawnguard and wait for my character there. So I went, and when I arrived he was already attacking all the Dawnguard. I helped put him on the ground, then I spoke to him again. He said he will read the Elder Scroll, and then he opens it while he is on the ground and it clips through his body from one hand to another, and he has been in that stance for awhile, and I can't continue the questline. I tried using Calm on him, but my character is a warrior and obviously isn't versed in magic so does not have enough magicka. So, what do I do? Any help would be appreciated.

Anyone?