Isran asks the Dragonborn to find and destroy the vampire masquerading as a Visiting Advisor to the Jarl of a radiant city; however, to avoid slandering the Dawnguard's name, permission must be gained from the Jarl to kill the creature or the guards will see it as murder. If you do kill the vampire without permission, you will complete the quest, but you will have to face the consequences if you are caught doing so.
Speak to the Jarl and explain the situation. They will state that proof is required before any action can be taken. Locate the Visiting Advisor, who can typically be found loitering in the main court. Pickpocketing his orders will reveal his true nature, but still carries a risk of being caught and getting a bounty in the process depending on the Dragonborn's Pickpocket skill. Especially if this is done near an Imperial or a Stormcloak commander, they will immediately attempt to arrest you when the pickpocket attempt fails.
Give this note to the Jarl and they will allow the Visiting Advisor to be killed without intervention from the guards. Once he is dead, return to Isran to complete the quest.
|A Jarl's Justice – DLC1RH07|
|10||Isran has sent me to <Alias=Capital> to warn <Alias=Jarl> of a vampire masquerading as a visiting advisor to <Alias.PronounObj=Jarl> court. I am to destroy the beast. If I fail to secure <Alias=Jarl>'s permission first, the guards will consider it a murder.
|255||I've destroyed the vampire in <Alias=Capital> masquerading as a visiting advisor to <Alias=Jarl>'s court.
|300||<Alias=Jarl> is no longer the Jarl of <Alias=Capital> and the vampire no longer poses a threat.
- The Visiting Advisor is one of the few characters that wears Vampire Robes, Vampire Gloves, a Vampire Hood and Vampire Boots.
- The spells Detect Life or Detect Dead do not reveal that the Visiting Advisor is a vampire. However, he still has the physical characteristics of a vampire (the spells affecting the undead have no effect on him).
- Isran might not have dialogue option to complete the quest, despite killing a vampire.