Claudius summons the help of Rosencratz and Guildenstern in Hamlet by William Shakespeare in Act II because the the two men had been friends with Hamlet while all of them were younger. Claudius is trying to discover whether Hamlet is merely feigning madness or is actually mad and is also trying to understand what the reasons might be for Hamlet's changes in behaviour. After Hamlet kills Polonius, Claudius asks Rosencrantz and Guildenstern to accompany Hamlet to England bearing a letter for the King of England. The letter asks the King of England to kill Hamlet. Hamlet edits the letter so that it instructs the King to kill Rosencrantz and Guildenstern. At the end of the play, the British Ambassador confirms that the King of England has killed the two men:

And our affairs from England come too late.
The ears are senseless that should give us hearing
To tell him his commandment is fulfill'd
That Rosencrantz and Guildenstern are dead.