In the darkness, the ghost speaks to Hamlet, claiming to be his father’s spirit, come to rouse Hamlet to revenge his death, a “foul and most unnatural murder” (I.v.25). Hamlet is appalled at the revelation that his father has been murdered, and the ghost tells him that as he slept in his garden, a villain poured poison into his ear—the very villain who now wears his crown, Claudius. Hamlet’s worst fears about his uncle are confirmed. “O my prophetic soul!” he cries (I.v.40). The ghost exhorts Hamlet to seek revenge, telling him that Claudius has corrupted Denmark and corrupted Gertrude, having taken her from the pure love of her first marriage and seduced her in the foul lust of their incestuous union. But the ghost urges Hamlet not to act against his mother in any way, telling him to “leave her to heaven” and to the pangs of her own conscience (I.v.86).

As dawn breaks, the ghost disappears. Intensely moved, Hamlet swears to remember and obey the ghost. Horatio and Marcellus arrive upon the scene and frantically ask Hamlet what has happened. Shaken and extremely agitated, he refuses to tell them, and insists that they swear upon his sword not to reveal what they have seen. He tells them further that he may pretend to be a madman, and he makes them swear not to give the slightest hint that they know anything about his motives. Three times the ghost’s voice echoes from beneath the ground, proclaiming, “Swear.” Horatio and Marcellus take the oath upon Hamlet’s sword, and the three men exit toward the castle. As they leave, Hamlet bemoans the responsibility he now carries: “The time is out of joint: O cursed spite / That ever I was born to set it right!” (I.v.189–190).

Polonius dispatches his servant Reynaldo to France with money and written notes for Laertes, also ordering him to inquire about and spy on Laertes’ personal life. He gives him explicit directions as to how to pursue his investigations, then sends him on his way. As Reynaldo leaves, Ophelia enters, visibly upset. She tells Polonius that Hamlet, unkempt and wild-eyed, has accosted her. Hamlet grabbed her, held her, and sighed heavily, but did not speak to her. Polonius says that Hamlet must be mad with his love for Ophelia, for she has distanced herself from him ever since Polonius ordered her to do so. Polonius speculates that this lovesickness might be the cause of Hamlet’s moodiness, and he hurries out to tell Claudius of his idea.

The ghost’s demand for Hamlet to seek revenge upon Claudius is the pivotal event of Act I. It sets the main plot of the play into motion and leads Hamlet to the idea of feigning madness, which becomes his primary mode of interacting with other people for most of the next three acts, as well as a major device Shakespeare uses to develop his character. Most important, it introduces the idea of retributive justice, the notion that sin must be returned with punishment. Claudius has committed a sin, and now, to restore balance to the kingdom, the sin must be punished. The idea of retribution haunts and goads characters throughout the play, functioning as an important motivation for action, spurring Claudius to guilt, Hamlet to the avoidance of suicide, and Laertes to murderous rage after the deaths of Ophelia and Polonius.

While Hamlet fits a genre called revenge tragedy, loosely following the form popularized by Thomas Kyd’s earlier Spanish Tragedy, it is unlike any other revenge tragedy in that it is more concerned with thought and moral questioning than with bloody action. One of the central tensions in the play comes from Hamlet’s inability to find any certain moral truths as he works his way toward revenge. Even in his first encounter with the ghost, Hamlet questions the appearances of things around him and worries whether he can trust his perceptions, doubting the authenticity of his father’s ghost and its tragic claim. Because he is contemplative to the point of obsession, Hamlet’s decision to feign madness, ostensibly in order to keep the other characters from guessing the motive for his behavior, will lead him at times perilously close to actual madness. In fact, it is impossible to say for certain whether or not Hamlet actually does go mad, and, if so, when his act becomes reality. We have already seen that Hamlet, though thoughtful by nature, also has an excitable streak, which makes him erratic, nervous, and unpredictable. In Act I, scene v, as the ghost disappears, Hamlet seems to have too much nervous energy to deal competently with the curious Horatio and Marcellus. He is already unsure of what to believe and what to do, and the tension of his uncertainty comes out in sprawling wordplay that makes him seem already slightly mad, calling the ghost names such as “truepenny” and “old mole” as it rumbles, “Swear,” from beneath the ground (I.v.152, I.v.164).

The short scene that begins Act II is divided into two parts, the first of which involves Polonius’s conversation with Reynaldo about Laertes and the second of which involves Polonius’s conversation with Ophelia about Hamlet. The scene serves to develop the character of Polonius, who is one of the most intriguing figures in Hamlet. Polonius can be interpreted as either a doddering fool or as a cunning manipulator, and he has been portrayed onstage as both. In this scene, as he carefully instructs Reynaldo in the art of snooping, he seems more the manipulator than the fool, though his obvious love of hearing his own voice leads him into some comical misphrasings (“And then, sir, does a this — a does — / what was I about to say? By the mass, I was about to say some / thing. Where did I leave?” [II.i.49–51]).

In his advice to Reynaldo, Polonius explicitly develops one of the themes of Hamlet, the idea that words can be used to bend and alter the truth. He explains to Reynaldo how to ask leading questions of Laertes’ acquaintances and how to phrase questions in a way that will seem inoffensive. As with Claudius, who manipulated the royal court with his speech in Act I, scene ii, words become a tool for influencing the minds of others and controlling their perception of the truth. Remember that Claudius killed King Hamlet by pouring poison into his ear. Shakespeare continually illustrates that words can function as poison in the ear as well. As the ghost says in Act I, scene v, Claudius has poisoned “the whole ear of Denmark” with his words (I.v.36). The running imagery of ears and hearing serves as an important symbol of the power of words to manipulate the truth.

Polonius’s conversation with Ophelia is important for several reasons. First, it illustrates how Hamlet has been behaving since his encounter with the ghost: he has made good on his promise to Horatio and is behaving as a madman. Though we learn about it only through her description, his emotional scene with Ophelia may stem in part from his general plan to feign insanity, and in part from real distress at seeing Ophelia, since she has recently spurned him. In addition, his mother’s marriage to Claudius seems to have shattered his opinion of women in general. The conversation also informs the audience that she has obeyed her father’s orders and broken off her relationship with Hamlet, confirming her docile nature and dependence on her father to tell her how to behave. And finally, the conversation engenders an important moment for the plot of the play: Polonius’s sudden idea that Hamlet’s melancholy and strange behavior may be due to his lovesickness for Ophelia. Though Polonius’s overly simple theory is obviously insufficient to explain Hamlet’s behavior, it does lead to several plot developments in the next few scenes, including Hamlet’s disastrous confrontation with Ophelia and Gertrude and Claudius’s decision to spy on Hamlet.