What is the alien but recognizable look that comes over Gatsby's face several times in chapter 7 of The Great Gatsby?

That look appears on Gatsby's face whenever he is faced with a truth that he would rather avoid.  The first time is when Tom mentions "drug stores".  This is a reference to the illegal alcohol sales Gatsby is involved in at various drug stores.  The second time is when Tom indicates that a man named Walter has some information on Gatsby betting illegally.  The look would best be described as the "hand in the cookie jar" look.  These are moments when Gatsby knows that he has been caught out, and realizes he might have trouble holding the high ground in his argument with Tom.