AU of Granada's "3 Gables" – those familiar with the ep will recognize more than those familiar with just the story.
He had taken beatings during Holmes's investigations before. It was never pleasant but at least it was for the sake of bringing about justice. This . . . this was for a matter alien to Holmes.
Love.
He had believed himself in love, or at least something akin to it. He thought she had loved him in return. Now he knew. She didn't love him because she was incapable of love – not as Holmes, who kept his emotions firmly in check – but because she had no heart. She had watched her hired men drive the toes of their rough boots into him, not even moving a finger to acknowledge his knowledge of her presence.
She feared he would expose her for the heartless wretch she was – he, who had helped keep the secrets of kings! The "very soul of discretion!" How little did she know him.
Ah, but he would write that account now! His identity he would protect but hers . . . hers should be plain to all of society. He was not a vengeful man but for her he would make an exception.
Afterwards he dragged himself back to Baker Street, dreading Holmes's reaction, and then realized he might have bigger problems to worry about, if the internal pain was any indicator.
His face bled; his stomach burned.