This quest is not available in game.
Kill Meven Korgal, the messenger, at the Crusader camp, then return any information you find to Executor Arren.
Reports from my superiors in Brill indicate that an agent of the Scarlet Crusade was dispatched from the Scarlet Monastery and sent here to Deathknell. According to the reports, the messenger possesses important information on his person. I do not have further details, but whatever it is, we must have it!
You're the most qualified person I have to send, <name>. Find that messenger and bring me whatever information you can find.