As Marlow's steamship approaches the inner station in a heavy fog, arrows begin to fly out from the jungle. The "pilgrims," or white passengers, fire blindly into the jungle with their rifles. Marlow blows the steam whistle on the ship and scares off the attackers. Then Marlow realizes the helmsman has been killed. In the next chapter the Russian explains that the Africans attacked the ship because they were afraid the ship was coming to take Kurtz away from them. Later the Russian divulges that Kurtz ordered the attack himself because he did not want to be taken away from his base of power.
As the steamboat progresses down the fog-covered river, the vessel is attacked by a barrage of flying arrows. Marlow spots a strange face in the brush on the riverbank and soon realizes that the land is covered with African natives prepared to launch a full attack. Although the crew manning the boat attempts to fight back with guns, their efforts are mostly fruitless, and blood spills across the boat's deck. The helmsman dies in the attack, and the agent is forced to take over the steering of the boat.
Ultimately, it is revealed that the African natives did not attack the boat impulsively; rather, Kurtz--who was paranoid that the Company wanted to remove him from his station and have him killed--ordered the natives to attack the boat in order to protect his own position.