Here's the breakdown:
* The Letter: Claudius writes a letter to the King of England, ostensibly to protect Hamlet. However, he secretly instructs the King to have Hamlet killed.
* The Execution: The letter details a plot by Hamlet to overthrow the King of England and usurp his throne. Claudius claims Hamlet is dangerous and must be silenced. This is a complete fabrication.
* Hamlet's Fate: Upon reaching England, Hamlet is expected to be executed by the King.
However, this plan backfires when Hamlet discovers the plot and swaps the letters, ensuring the execution of Rosencrantz and Guildenstern instead.