11. What does the call from Slagle tell the reader?

Slagle's call confirms that Gatsby was involved in some questionable activities, namely, passing stolen or counterfeit bonds.

“Young Parke’s in trouble,” he said rapidly. “They picked him up when he handed the bonds over the counter. They got a circular from New York giving ’em the numbers just five minutes before. What d’you know about that, hey? You never can tell in these hick towns ——”