“While Mordecai was sitting in the royal courtyard, two of the king’s eunuchs, Bigthan and Terseh, who were the chief bodyguards, became angry. They conspired to assassinate King Artaxerxes. This matter became known to Mordecai, who warned Queen Esther. She, in turn, revealed the plot to the king in the name of Mordecai. When the affair was investigated and found to be true, the men were both hanged. Then the king ordered a memorandum to be deposited in the royal library in praise of the goodwill shown by Mordecai. It was recorded in the book of the annals in the presence of the king.”
The names of the 2 eunuchs are only in the Hebrew text, not the Greek text. Eunuchs were personal bodyguards. Perhaps this relates to the preliminary Greek text about the plot against the king, where Mordecai heard 2 eunuchs plotting to kill the king. There they confessed and were executed. It sounds very similar. Except here, Mordecai told Esther who then told the king. Here it is very clearly recorded in the annals of the king.