The Inseco company participated in a tender for the supply of equipment for the oil industry in the amount of forty-seven million dollars and, according to all forecasts, should have won. However, the tender was unexpectedly won by an unknown shell company: a few hours before the auction, its management offered more favorable conditions. Inseco vice-president Vadim Tregubov found out that competitors had reduced the price by only two thousand dollars. This circumstance led him to believe that someone from his inner circle leaked information to competitors about the amount included in the tender application. But who? The businessman turned to the famous detective Drongo with this question...