There was a darkness spreading over his mind. He could feel it, a cold trickle down his spine. It was all he could see when he closed his eyes. He felt it burning there, constantly. And he was not unaware that the others were beginning to notice.
Boromir bowed his head and walked away. Nobody noted his departure. He walked away into the woods. He began to pick up bits of wood to stop himself from screaming. He wondered that the wood did not catch fire from his hands; the image burned so brightly behind his eyes, he wondered he did not set the whole forest alight. He was breathing heavily and his footfalls were loud in the silence of the trees.
Please, let me be, he heard himself plead, and he did not know if he spoke aloud or only in his mind. There was no response, ever. Nothing ever acknowledged his silent cries for help, for relief. The darkness came upon him so suddenly he almost fell to his knees. End it, he pleaded. If you will not let me go, end it. Please…
Frodo was standing not far from him as the blaze of dark desire washed over him. The Halfling had not seen him, so it was a simple matter to step quietly closer.
"None of you should wander alone," Boromir heard himself say. "You least of all. So much depends on you." He could hear the disgust and scorn in his voice, and some part of his mind protested. But the image burned all the brighter, and burned the reasonable part of him away.
"I know why you seek solitude." Was he speaking to Frodo or himself? He could hardly tell, he could hardly see. The darkness was all-consuming now. "You bear a heavy burden; I see it day by day." Still the Hobbit said nothing. And the desire burned on. "There are other ways, Frodo. Other paths we might take."
"…would seem like wisdom, but for the warning in my heart."
It took a moment for Boromir to hear Frodo's voice. It came to him as if from far away, across a void, perhaps, a void of darkness, at the edge of which he tipped precariously.
"Warning?" His voice was pregnant with the cruel desire that fuelled him. He wondered not why Frodo recoiled, but the desire asked the question. "Why do you recoil, I am no thief." Let it end, please. Let me be.
He knew not what he said next as the darkness filled his mind. The image burned in the darkness: himself, holding the Ring at last, aloft for all to see that it was he, Boromir of Gondor, who possessed the One Ring, that it was he, Boromir of Gondor who protected them against the evil in Mordor that lay sleeping. But can you protect them from yourself?
There was a flash of pain that cut through this darkest hour. The desire was no longer there. There was no darkness. His mind was clear, and he was shaking. Frodo was gone.
"What have I done?" he whispered. "Please, Frodo. Please, please. Frodo, I'm sorry!" He screamed the last words to the empty air around him. Let it end, oh please, let me be. Now it was not the darkness that haunted him, but the guilt. He hated himself. What have I done? "I'm sorry. I'm so sorry." Please forgive me, before it ends.
Boromir cried out again and again, seeking forgiveness. But no one ever heard…