Mordecai was the son of Jair, of the tribe of Benjamin. He resided at Susa, the metropolos of Persia at the time when Xerxes was its king. He adopted his cousin Esther who was an orphan child and brought her up as his own daughter. When Esther grew up, Xerxes made her his queen as replacement to his deposed wife Vashti and Mordecai was promoted to some office in his court, a position that led him to uncover a plot against the king's life one day.
During the time Mordecai was sitting at the king's gate, Bigthana and Teresh, two of the king's officers who guarded the doorway, became angry and conspired to assassinate King Xerxes. 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 hanged on a gallows. All this was recorded in the book of the annals in the presence of the king.
This deed was to have some interesting effects in the future.
A man named Haman, who had been made prime minister at the court of Xerxes, was infuriated that Mordecai refused to bow down before him. His hatred for the man increased when he found himself having to honor Mordecai one day, when the king read what had been recorded about Modecai's assistance in foiling the plot against him. This hatred quickly turned into a desire to see the destruction of all the Jewish exiles throughout the Persian empire. Word of this scheme reached the ears of Mordecai, who promptly informed his cousin - now Queen. By her wise and bold intervention the scheme was frustrated. The Jews were delivered from destruction, Mordecai was raised to a high rank, and Haman was executed on the very same gallows he had by erected in anticipation for Mordecai.