Grand Party.

He sighed when he got the information and said, "I am disappointed. I am very disappointed."

He is disappointed in Delia for a lot of reasons. The first and main reason is that he hates schemes and plots. The second reason he is disappointed is because she is doing this despite him warning her not to. 

But he didn't stop the party because he didn't want to jump to conclusions. He would like to think he has misjudged her, so he wants to see what she is up to. 

After all, it will be highly disrespectful to him if she actually went ahead to scheme and plot immediately after he warned her not to. Even he thinks it is a tad unbelievable. 

He would like to think this is all a misunderstanding on his part. Besides, he also wants to know the extent of her scheme so that he will be able to mete out appropriate punishment. 

So he didn't stop the party from holding. He just paid close attention to everything going on.