In the Chief of War episode 7, Marley and Metcalfe are two British travelers who visit the Hawaiian island.
Upon arrival, their eyes are glued to the land of sandalwood trees and its riches. They are presented to Kamehameha, who treats them like a guest. This alerts Ka'iana about a greater threat looming with this colonial presence.
Ka'iana believes the foreigners to be a threat to the people and leads an attack with a handful of warriors. He boards Metcalfe's boat, intending to abduct or kill them. But he is interrupted by Kamehameha.
Meanwhile, Metcalfe attacks a Hawaiian village, and during this time, Marley falls overboard and drowns. He isn't seen after that, keeping his fate still unknown in the Chief of War.
What happened to Marley in the Chief of War Episode 7?

In Chief of War, Marley is one of Captain Metcalfe’s men, who, upon his arrival on the Hawaiian island, becomes greedy for the resources, especially the sandalwood trees. Marley and Metcalfe consider the Islanders nothing but a handful of mindless, savage people.
When a Hawaiian boy intervenes, they turn to arms but are easily outnumbered by the local people. They are then presented to King Kamehameha, who, instead of punishing them, treats them as guests and welcomes them as part of his peaceful treaty.
However, Ka'iana questions the credibility of the foreign travellers, as he is aware of their manipulation and greed. He also tries to convince Kamehameha not to be naive and treat them nicely. Ka'iana was sure that they had come to exploit and colonise the island, and he saw them as a greater and even darker threat than the rivals within the island.
Ka'iana took a major step without Kamehameha's permission to avoid the dark fate. With some warriors, he boards Metcalfe's boat with a plan to kill him and his men on the journey. However, the king intervenes in time, failing Ka'iana's mission. During this chaos, Marley is forced overboard and falls into the ocean. This comes as a twist, as we don't know whether he dies or survives.
But this wasn't the end. What was awaited at the shore was beyond anyone's imagination.
What happened by the end of episode 7 of Chief of War?

As Marley falls into the water, Captain Metcalfe’s men continue to a peaceful Hawaiian village. There, they launch attacks, loading their canons with nail-filled canisters and firing at civilians. The villagers die, with their families torn apart, suggesting a display of colonial brutality. Vai also dies while protecting a little girl, and Ka'iana fails to save any of them despite prior suspicions.
This event puts Kamehameha under immense guilt. He feels that his beliefs led to the massive loss. He also feels responsible for causing severe damage to his people for a policy he didn't want to violate. He could have prevented the attack and was also warned for trusting the white men, but his inability to act in time led to mass destruction.