"Then Esther summoned Hathach, one of the king's eunuchs assigned to attend her, and ordered him to find out what was troubling Mordecai and why." NIV translation
When Mordecai refused the clothes, Esther knew that it was serious. So, she sent a servant to question Mordecai.
"So Hathach went out to Mordecai in the open square of the city in front of the king's gate. Mordecai told him everything that had happened to him, including the exact amount of money Haman had promised to pay into the royal treasury for the destruction of the Jews." NIV translation
So, when Hathach went to Mordecai, he was told of Haman's plan to kill all of the Jews. He even told him of the money that Haman was willing to offer.
"He also gave him a copy of the text of the edict for the annihilation, which had been published in Susa, to show to Esther and explain it to her, and he told him to urge her to go into the king's presence to beg for mercy and plead with him for her people." NIV translation
Mordecai also sent a copy of the edict with Hathach and asked him to explain it to her. He then asked for Esther to go to the king and beg for mercy on behalf of the Jews. This is big because she will be identifying herself as a Jew and, in doing so, the king's order would apply to her.
"Hathach went back and reported to Esther what Mordecai had said. Then she instructed him to say to Mordecai, 'All the king's officials and the people of the royal provinces know that for any man or woman who approaches the king in the inner court without being summoned the king has but one law: that he be put to death. The only exception to this is for the king to extend the gold scepter to him and spare his life. But thirty days have passed since I was called to go to the king.'" NIV translation
So, Esther sends Hathach back to remind Mordecai that, if she does what he asked, she could be killed. The custom of the king reminds us of the Holy of Holies in the Temple. Just as nobody could approach the king in the inner court, the high priest could only enter the Holy of Holies once each year. The king extending the gold scepter is a wonderful reminder of how Jesus extended his arms on the cross to buy our pardon.