There is a subplot in the Purim story that finds two of the King’s men planning to murder him:

In those days, while Mordechai sat at the king's gate, Bigtan and Teresh, two of the king's chamberlains from the threshold guards, became angry and planned to assassinate King Achashverosh. 

The matter became known to Mordechai and he informed Queen Esther. Esther then informed the king of it in Mordechai's name. (Chapter 2, Verses 21, 22).

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