“What about it?” said Gatsby politely. “I guess your friend Walter Chase wasn’t too proud to come in on it.”
Gatsby is done pretending that all of his money came through legal means, since it is clear Tom found enough information about him. But then he points out that Walter Chase, who we can assume is one of Tom’s “old money” buddies, was involved in the operation as well. This proves that new money people are not the only ones that take part in illegal activities, as much as Tom believes otherwise.
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