Sentence:  “But marriage in secret, Nikolay Vsyevolodovitch — a fatal secret. I receive money from you, and I'm suddenly asked the question, 'What's that money for?' My hands are tied; I cannot answer to the <WSD>detriment</WSD> of my sister, to the detriment of the family honour.” 
Meaning of the word marked with <WSD> tags:  Harm, hurt, damage.