Shakespeare's Hamlet deals a lot with plotting and scheming. Who sets these plans in motion and to what ends?
Claudius is the plotter and schemer par excellence. He plots and schemes to become king by murdering his brother. Then he manages to marry his brother's widow and to get elected king, thereby cheating young Hamlet out of his rightful inheritance of the crown. When Hamlet returns from Wittenberg, Claudius keeps him a virtual prisoner at Elsinore because he naturally suspects that his nephew might be thinking of plotting to overthrow him. Hamlet is young, melancholy, solitary, introspective. Claudius misinterprets Hamlet's moodiness as dangerous brooding. The King's fears for his safety motivate him to spy on Hamlet by every possible means. He uses Polonius, Ophelia, Gertrude, Rosencrantz, Guildenstern. and no doubt countless courtiers and members of the household staff to try to find out what Hamlet is thinking and planning. Hamlet decides to pretend to be crazy, mainly in order to keep the King from guessing what he knows and what he is planning. So it is Claudius who sets the plans in motion for the purpose of protecting his life and his position as King. It takes Hamlet a long time to grow up, so to speak, and to gather the resolution to take the action he is obliged to take, which is to kill his villainous uncle. Hamlet's procrastination causes tragedy for many besides himself. By the end of the play all the principals are dead except for Horatio.
Claudius does quite a bit of scheming in Hamlet and he sets the plot in motion by murdering Hamlet's father and then working to get rid of Hamlet, but Hamlet himself also is great schemer. For all that Hamlet tells Horatio there's more to the universe that mere empirical science (which he calls philosophy), he himself is careful and scientific about testing the hypothesis that the ghost he met is actually his father and not a spirit sent by Satan to tempt him to murder an innocent man. Hamlet wants to find signs of guilt in Claudius to confirm he is a murderer. To do this, Hamlet has the players (actors) who come to court put on a play called The Mousetrap in which they enact in pantomime the murder the ghost describes. When Hamlet sees Claudius's frightened reaction, he knows the ghost has told him the truth.
Hamlet also counterplots to foil Claudius's devious plans. For example, he opens the letter saying he should be killed as soon as he arrives in England, and changes it so that the carriers of it, the courtiers Rosencrantz and Guildenstern, are killed instead. Hamlet himself then returns to Denmark to confront his nemesis.