The System - S1-E2
Stupidity: The plot hinges on the fact that even Frank Marley's most trusted man would doubt him because of his actions, but he and Marley counted the money together; he should know that Marley was right and the amount declared was not lower than the actual money deposited. Instead, he is fooled like everyone else by the extra 25K$ planted by the IMF team. Their plan can't work unless he is oblivious and/or forgetful.