The Surge

The Surge is the third and final mission of The Knife of Dunwall DLC.

Briefing
''Delilah is a powerful witch who leads a coven that has moved into the ruins of Brigmore Manor. You've returned to your hidden base in the Flooded District to plan your next move.''

Infiltration
When Daud enters the Flooded District via the Rudshore Gate, he is greeted by a different person depending on his chaos level: if Daud's chaos is low, Billie Lurk will appear to report to him that their hideout has been overrun by Overseers. If Daud's chaos is high, an unnamed Whaler will give him the same information.

Overseer Leonard Hume, leader of the attack, has overtaken the Commerce Building and has instructed his Overseers to interrogate captured Whalers. If Daud so chooses, he can search out the imprisoned Whalers and free them before advancing to his personal quarters, where Hume has set up his command station.

In order to progress, Daud must seek out the Overseer Assault plans, which will enable the assassins to stop the rest of the invading Overseers. The plans are located in one of the abandoned buildings in the area. This particular one has two floors, the first of which is an Overseer outpost.

Revelation
Once Hume has been eliminated and the plans are located, Daud can return to the area outside the Commerce Building where Billie will appear, saying that the Overseers have been pushed back from their base. (If Daud neutralizes Hume non-lethally, Billie will also inform him that the Overseer has been taken away for questioning.)

When Daud asks how the Overseers knew of their location, Billie reveals a startling truth: She cooperated with Delilah to bring the Overseers to the Flooded District in an effort to assassinate Daud (whom she claimed has "been slipping" since the assassination of Empress Jessamine Kaldwin) and usurp his position.

Delilah Copperspoon appears briefly to verify the claim, her response to Daud and Billie varying based on Billie's forthcoming reaction. If Daud's chaos is low at the end of the mission, Billie will express regret at her actions, saying she misjudged him. If Daud's chaos is high, Billie will stand behind her choice and challenge Daud to a duel. In both cases, Daud can choose to spare or kill her, completing the mission.

Non-Lethal Alternative
Daud must simply neutralize the target using a non-lethal method (choking or sleep dart), which will cause the mission to advance. Choosing to capture rather than kill the remaining Overseers and then sparing Billie will complete the non-lethal playthrough.

Side Objectives

 * Free all the captured assassins
 * Eliminate all six musical Overseers

Special Actions

 * Killed Billie Lurk
 * Spared Billie Lurk
 * Rescued All Your Assassins
 * Eliminated All the Overseers Armed With Music Boxes

General Mission Notes

 * If Daud successfully frees all of the captured assassins before confronting Overseer Hume, using the Summon Assassin power in the main room will result in several assassins coming to his aid, instead of one.
 * If Daud frees at least one of the assassins before going for Overseer Hume (in low chaos), Billie will help fight Hume alongside Daud.
 * If Daud kills one of the captured assassins, the side mission will fail and will be replaced with eliminating the Overseers with music boxes.

Trivia

 * Throughout the mission, Overseers can be heard discussing the condition of the Abbey of the Everyman.
 * The name of this mission in the French version translates into "Witch-hunt".
 * If Daud uses the Summon Assassin power during his duel with Billie Lurk, Lurk will insult him and claim that she is 'better than any of these fools'.
 * The Heart already alludes to the events of this mission in the main game. The remains of the attack is also seen in the main game, mentioned on notes found during The Flooded District; orders for the attack, notes from an attacker warning his brethren, interrogation notes from the aftermath, and research notes the Whalers made studying their opponents.