Graham got worked up imagining Kate would get hurt because of Henry's malicious plan. He was thinking of many ways to protect her, whether it was out of pity or love; he didn't really care. As long as Kate was safe, then Graham would be at peace.
Kate went silent after that, and Graham was relieved, thinking that Kate finally took his side after he told her everything. He had been hesitating at first because he didn't want to break Kate's heart, and he still had a brotherly bond towards Henry. But this might be the end of everything…
"Kate?"
"What nonsense are you spouting about, Mr. Hubbard?" Kate asked.
"N—Nonsense?!" Graham was stunned. "I didn't speak nonsense! It's all true! I'm not lying to you!"