During the time Mordecai was sitting at the king's gate, Bigthana and Teresh, two of the king's officers1 who guarded the doorway, became angry2 and conspired to assassinate King Xerxes.
References for Esther 2:21
But Mordecai found out about the plot and told Queen Esther, who in turn reported it to the king, giving credit to Mordecai.
And when the report was investigated and found to be true, the two officials were hanged3 on a gallows. All this was recorded in the book of the annals4 in the presence of the king.5
References for Esther 2:23