"Do you want to destroy the harmony of this family? Destroy the relationship between your sister and her? Or even... put herself in a very embarrassing situation..."
Harry's words were a naked threat. His tone carried a double entendre. On one level, he implied that Elena's actions would shatter family harmony; on another, his words served as a veiled warning, reminding her that she already knew something of what he had done that night.
In this way, Harry could advance or retreat at will, using his words to test whether Elena would be frightened by him or reveal that she knew of his actions that night.
"I... I... why do I hate you... you... you should know better than me! Brother-in-law... what did you do to me... that night... why... why I..." Elena stammered, then suddenly fell silent as her whole body trembled and her face flushed with shame.