In those days, while Mordecai was sitting at the king's gate, Bigthan and Teresh, two of the king's eunuchs, who guarded the threshold, became angry and conspired to assassinate King Ahasuerus.
References for Esther 2:21
But the matter came to the knowledge of Mordecai, and he told it to Queen Esther, and Esther told the king in the name of Mordecai.
When the affair was investigated and found to be so, both the men were hanged on the gallows. It was recorded in the book of the annals in the presence of the king.