Following the events of Murder On The Border, Overseer Siv calls the player to the command centre to discuss an urgent matter: improving the security of the fort. They agree that the fort needs guards, especially since the Raptor has wandered in unchallenged. Siv works on the guard problem while the player talks to the Raptor, who informs them that he's come to help them with a problem: there's a large group of undead that have been sighted to the north of the fort, and if they attack, the fort will be done for. The player and the Raptor deal with the undead, but that doesn't solve the problem: the player still needs to fortify the walls.
The player talks to Bill, who's been drawing up plans for a new inn. They explain the problem, and Bill gets some logs moved into place to help fortify the walls. Once the player's turned the logs into big spikes, they talk to Siv, who's found some guards. However, the guards can't be housed in the command centre, so Siv suggests building a guardhouse. The player talks to Bill and convinces him to convert his inn plans into a guardhouse, which they then build. Once that's done, Siv says that the guards should be there soon, but they'll need a captain. The player wants the Raptor to be the captain, but the Raptor is very against that idea.
The four guards arrive, and the player is not over the moon at this- at first they think the guards are Black Knights, but Siv explains that they're actually former members of the Dark Warriors, a bandit gang. Their leader was killed by a Zamorakian, and between that and the recent mammoth attacks, they want out of the Wilderness, but no kingdom will accept them. They'll work for room and board, so the player agrees to give them a shot. Talking to the guards gives a bit more detail- during the Zamorakian Civil War, all the bandit gangs were either recruited by one of the two sides or killed. The Dark Warriors' leader refused to take part in the war, which is why they killed him (and also why the Dark Warriors' Fortress doesn't have any living residents now).
The Raptor tells the player to meet him at the north gate so they can search for the source of the undead. After killing more undead, they find the source- an inexplicably open crypt. Inside the crypt, they find Zemouregal, who admits that he summoned the undead as a distraction from his real plan. He destroys the bridge between them and summons more undead to fight the Raptor and the player; outnumbered, the Raptor calls for a retreat.
Back at the fort, the Raptor tells the player that he's going to stay in the fort: Zemouregal is eventually going to attack, and if the fort falls, the kingdom will be in serious danger. The player is surprised, saying that the Raptor doesn't seem like someone who'd care about that, but the Raptor tells them that they don't know anything about him. The player wants the Raptor to be the captain of the guards, but the Raptor still refuses, though the player says that he can still lead by example. The Raptor makes it clear that he isn't there to be in charge, and if the guards learn by watching him, fine- but if they betray the fort, he'll kill them. He adds that they need to cull the undead in the crypt so their numbers don't get too big, and when the player's ready to do that, they should come talk to him. With that, quest complete!
(Post-quest, talking to the Raptor has him tell the player his plan for dealing with the undead: he'll give the player a number to kill, and then he'll match it, so that way they can track their kills. When asked why the player should do this, the Raptor says he has a lot of Slayer equipment and will share it with the player if they do as he asks. When pointed out that this makes him a Slayer Master, he says this is not in fact the case, because the Slayer Masters just sit back and watch, which he doesn't.)
