I have posted two versions, one vague and one very specific (just in case the shorter version doesn't work) SHORT SOLUTION -Listen to the full dialogue between Malkus and Dexion. -Kill Malkus, do not loot. -DO NOT kill the other vampire. (If you have any followers, it would be wise to have them wait down the steps or something - to refrain from attacking the other vampire) -Leave Forbears' Holdout -Wait for 24 (in-game...) hours -Re-enter Forbears' Holdout -Dexion should be outside of the magical barrier, having killed the other vampire for you. -Loot Malkus (for the Weystone Focus) -DO NOT de-activate the magical barrier -Speak to Dexion and all should be well. -Leave the Holdout and the quest marker to deactivate the magical barrier will be gone after he reads the elder scroll. DETAILED SOLUTION (If simple solutions fails) -Leaving Dawnguard, I did NOT have Serana follow me. -I entered the holdout and cleared my way up to the stairs where Dexion is being held. -I have a mod follower, whom I told to wait before going up the stairs to the magical barrier. (to keep from attacking anyone) -I snuck up the stairs (leading to the magical barrier) without being seen and listened to the full dialogue between Malkus and Dexion. -Without being noticed, I killed Malkus with my bow and DID NOT kill the other vampire there. -I did not loot Malkus. -I left the holdout (while sneaking so the other vampire did not see me) and, from right outside, I waited 24 (in-game...) hours. -I went back in to find Dexion OUTSIDE of the magical barrier and he had killed the other vampire. -I looted the Weystone Focus from Malkus but DID NOT use it to remove the barrier. -I was able to walk up to Dexion and speak to him safely. -The quest marker to remove the magical barrier was removed after Dexion read the Elder Scroll. If there are any questions, let me know.