keeping with the virtues of his culture. He and his brother are warriors, proud and strong:

You know we were men of family, belonging to a ruling race, and more fit than any to carry on our right shoulder the emblem of power. And in the time of prosperity Si Dendring showed us favor, as we, in time of sorrow, had showed to him the faithfulness of our courage.

Their lives are thrown into turmoil when Arsat falls in love with Diamelen, the wife of a powerful noble, Inchi Midah. Arsat's brother counsels him to stay away from the woman, but Arsat and Diamelen continue to meet in secret, their forbidden love growing until Arsat can no longer bear to live without her. When Arsat's brother realizes the strength of Arsat's love, he determines to help Arsat steal Diamelen so the two can be together:

We are of a people who take what they want—like you whites. There is a time when a man should forget loyalty and respect. Might and authority are given to rulers, but to all men is given love and strength and courage. My brother said, "You shall take her from their midst. We are two who are like one." And I answered, "Let it be soon, for I find no warmth in sunlight that does not shine upon her."

The brothers concoct a plot to take Diamelen under cover of darkness, while her husband and the other courtiers are distracted. The plot is successful, and Arsat and Diamelen make their escape in a canoe, which Arsat's brother steers.

Now that action has been taken, Arsat's dilemma becomes clear, for his brother has sacrificed his own safety and place in society by assisting him in the kidnap of Diamelen. The rajah's men will be coming after them to punish the brothers and take Diamelen back, and Arsat may have to choose between defending the brother who has always helped him and fleeing with the woman he loves. He blindly hopes that it will not come to this and that somehow they will all escape to safety:

I longed to be with her in a safe place beyond the reach of men's anger and of women's spite. My love was so great, that I thought it could guide me to a country where death was unknown[.]

As the day dawns, the threat of pursuit becomes more urgent, and Arsat and his brother paddle as swiftly as possible away from Si Dendring's territory. Arsat is giddy with love for Diamelen and fear of the consequences of his actions, and he knows he would not have made it half so far without help from his brother:

My brother loved me. He dipped his paddle without a splash . . . All my strength and all my spirit were in my hands that held the paddle . . . There was no better paddler, no better steersman than my brother . . . He was strong. He was brave. He knew no fear and no fatigue . . . My brother!

When the rajah's men catch up with the little group where they have beached on the riverbank, Arsat's brother tells Arsat to take Diamelen and run through the jungle to a place where another canoe can be found. He promises to hold off the rajah's men and then run to join Arsat and Diamelen, and they will all escape again further up the river. Arsat does as his brother commands and finds the canoe his brother described. Throwing Diamelen into it, he waits breathlessly for his brother to appear so they can get away together, but when his brother does appear, he is surrounded by the rajah's men, and Arsat must choose in that instant whether to try and rescue his brother or to flee in the canoe with Diamelen.

When I looked back I saw that my brother had fallen. He fell and was up again, but the men were closing round him. He shouted, "I am coming!" The men were close to him. I looked. Many men. Then I looked at her. Tuan, I pushed the canoe!

Arsat's brother screams his name in horror and grief as he watches Arsat paddle away from him, leaving him to die at the hands of the rajah's men. Arsat has been haunted by his decision ever since, and yet his love for Diamelen was more powerful than his love for his brother:

I never turned back. I heard him calling my name again with a great shriek, as when life is going out together with the voice—and I never turned my head. My own name! . . . My brother! Three times he called—but I was not afraid of life. Was she not there in that canoe? And could I not with her find a country where death is forgotten—where death is unknown?

Arsat and Diamelen come to live at the lagoon in an abandoned fisherman's hut, cut off from the rivers which serve as the highways of their people, isolated from all society, exiled from their community, and surviving only on their love for each other. This "country where death is unknown" is a strange, silent place, where life seems to be on hold. Conrad's rich imagery suggests the lagoon's oppressive, claustrophobic stillness, painting it as a place that life passes by, where time does not move and the world seems to hold its breath.

Now Diamelen lies dying of fever. Death has come to their small world, and Arsat must face the consequences of his actions. In confessing his guilt to the white man, he accepts that betraying his brother, after everything his brother had done for him, was monstrous. Love compelled him to do it, and love insulated him from his guilt for all these years, but the object of his love is dying, and Arsat's guilt about his brother's death is rushing in to take love's place.

'I had her there! I had her! To get her I would have faced all mankind. But I had her—and—'

[...]

Arsat burst out with an intense whispering violence—

'What did I care who died? I wanted peace in my own heart.'

Arsat's sin is now fully revealed in the ruthlessness of his choice to abandon his brother, and by finally admitting to his lack of remorse, Arsat's confession is complete. He goes into the hut to check on Diamelen, only to find that she has succumbed to her fever. Having admitted his guilt and lost his justification for it in one stroke, Arsat must do penance for abandoning his brother. He can no longer remain in the lagoon's "breathless stillness," cut off from life, and indeed, life now seems to be coming to meet him:

The breeze freshened; a great brilliance burst upon the lagoon, sparkled on the rippling water. The forests came out of the clear shadows of the morning, became distinct, as if they had rushed nearer—to stop short in a great stir of leaves, of nodding boughs, of swaying branches.

Arsat must rejoin the world and pay for his crimes. He will return to his community, where he intends to die fighting the men who killed his brother, sacrificing himself as justice demands:

We were sons of the same mother—and I left him in the midst of enemies; but I am going back now.

The story ends with the white man leaving the lagoon, and seeing Arsat standing forlorn on its banks, stripped of all he loves and with nothing now to look forward to but death.

Initially, Arsat's brother is his emotional confidant. Arsat's brother advised him to be patient and wait until Si Dendring died before seeking a relationship with Diamelen. However, Arsat becomes impatient and confides in his brother, who becomes his co-conspirator as the two warriors plan on escaping the village with Diamelen. Arsat's brother selflessly risks his life helping his brother escape with Diamelen. When the war party begins closing in on them, Arsat's brother sacrifices himself by attempting to stall the search party. As Arsat and Diamelen escape unharmed, Arsat's brother is overtaken and killed by the war party. Essentially, Arsat's brother courageously risked his life for his brother's future. At the end of the short story, Diamelen dies, and Arsat seeks redemption by returning to his village to fight against the men who killed his brother. Arsat's brother plays the role of savior and is portrayed as a fearless, loyal individual who was willing to die for his brother's happiness. 

I think that the role of Arsat's brother is both direct and complex.  On the direct side, his role is to be the source of help and strength for Arsat.  It is the brother that provides counsel to Arsat when he struggles for initially what to do and then it is the brother who offers him help when he realizes what he feels he must do.  Arsat's brother is the reason that Arsat and Diamelen are able to run away together, as he offers up himself as the sacrifice to the pursuing guards.

In this characterization, there is also complexity. Arsat's brother represents the purest of the characters in the short story. His role is to thus become the compass by which Arsat and Diamelen are to be assessed. When Diamelen dies, Arsat calibrates his own sense of right and wrong to pursue vengeance for his brother. Arsat's brother's role is one of nobility, representing how the modern setting is one in which the purest of characters are not able to fully enjoy the benefits of life as they are the ones who end up sacrificing the most. In this, Arsat's brother occupies a thematic role that is of significant importance to this short story.