Berthold has been newly hired to work as a counselor for Henry IV, a man who has gone mad and believes that he is Henry IV of Germany back in the 11th century. The other three couselors show Berthold around the throne room and make fun of his ignorance. It turns out that Berthold studied his history on the wrong Henry IV, but the others tell him it does not matter because they themselves are not always sure of their roles. They promise to help him learn the proper material in order to play his role better.
Harold points to the pictures of Henry IV and the Marchioness and asks Berthold if he knows who they are. Berthold is surprised to see the two modern painting in the middle of all the antiquity, and inquires about them. Landolph informs him that Henry IV pretends that the paintings are mirrors. A little frightened by the concept, Berthold worries that he might go mad if he stays and works in the castle.
Soon John enters, a man in twentieth century clothes, and informs them that the Marchioness has arrived along with several gentlemen and her daughter Frida. The other gentlemen turn out to be Belcredi, her current lover, Charles Di Nolli, her daughter's fiance, and a Dr. Genoni who does psychoanalysis.
They arrive in the throne room and Donna Matilda immediately spots the painting on herself. She is astonished that the painting, done in her youth, looks exactly like her daughter does. Belcredi and the Doctor are not at all astonished that the daughter resembles her mother so much, but the others get mad at Belcredi when he points this out. It turns out that the painting was given to Henry IV about four years after the accident that made him go mad, as a gift from the Marchioness.
The doctor starts to ask questions about the past in order to better analyze Henry's condition. He learns that Henry IV, Belcredi, and the Marchioness were all taking part in a pageant, dressed up for their parts. As a result, they all had the paintings done while in costume. After Henry IV fell from his horse and went mad, his sister (Di Nolli's mother) requested that Donna Matilda give her picture to him, which she did.
The doctor then starts to learn about what happened at the pageant. Donna Matilda assumed the role of the Marchioness of Tuscany, thereby causing Henry IV to choose his role so as to be near her. He was courting her at the time, but he was so serious that she merely laughed at him when he approached her. Apparently it became a public affair, and the other men present laughed at him as well. Belcredi then informs the doctor that Henry IV used to be the type of man that would let himself go when playing a role, able to forget his real self in the process.
After the accident, where Henry fell from his horse and hit his head, they took him to a villa. As a joke, the other actors continued playing their roles when he woke up. It was only a few moments later that they realized while still wearing their masks that Henry IV was no longer wearing a mask, but playing his role in deadly earnest. Belcredi laughs and points out to them that Di Nolli was only a child at the time, and that he and Donna Matilda have gotten old over the years, whereas Henry IV is permanently fixed in time.
Berthold rushes into the room, surprising them all. He has managed to get Henry IV mad at him, and as a result Harold and Landolph propose that the guests visit Henry IV in order to make him forget about Berthold. They agree, and costumes are soon brought for them. After they get dressed, Henry IV enters and looks at them. He first calls Belcredi "Peter Damiani" and pretends that they are who they are dressed up to be. However, he soon digresses and remarks on the fact that it is much easier to go through life having everything fixed rather than not knowing what will happen. He also comments on the fact that being Henry IV is his reality, whereas they see him as someone pretending to be Henry IV.
After his speech, he starts to act mad and pretends that he is really Henry IV. Historically, Henry IV fought with Pope Gregory VII and was excommunicated, and as a result he was forced to crawl into Rome and beg forgiveness. Henry IV asks to be allowed to meet the Pope. He is further convinced that the Pope is using magic against him, magic that has made him eternally twenty-six years old, the same age as in the portrait. Henry IV therefore begs the doctor and Donna Matilda to intercede with the Pope on his behalf. He bows grandly and exits, leaving Donna Matilda in a state of tears.
Henry IV is a play concerned with the concept of a mask on a face. This concept has many different interpretations and is elaborated on in several ways. Foremost the mask is worn by the sufferer to keep out prying eyes. The mask also serves to fix oneself in time; by choosing an historical character Henry IV is able to live out his life at the same age. The mask also deals with the merger of actor and character, such as when Henry IV took off his mask but still believed he was Henry IV: "I shall never forget that scene - all our masked faces hideous and terrified gazing at him, at that terrible mask on his face, which was no longer a mask, but madness, madness personified."
This quote fits in well with many of Pirandello's beliefs. Donna Matilda is describing the masquerade right after Henry IV woke up, where everyone else is wearing a mask except Henry. Because he is not wearing a mask, he is accused of being mad. What Pirandello is saying is that madmen tell the truth, but it is a truth that no one else wants to hear. Thus, society forces people to wear masks in order to conform. When Henry IV emerges without a mask, he is more terrifying to the others because he finally free of the inhibiting masks that they wear.
One of the themes of this play is the exploration of ways to fixate time. There are three ways shown to fix oneself in time: you can become an actor and identify yourself with history, become a portrait as in the pictures of Henry IV and the Marchioness, or you can go mad. Identifying yourself with history has the advantage that your role in time is pre-ordained. You are thus able to go through life without ever having to make a decision, a desire that Pirandello believes many people have. Becoming a portrait also stops time, "Because a portrait is always there fixed in the twinkling of an eye", as the Doctor explains. The third method is to go mad. By going mad you are able to act any way that you wish, essentially freeing yourself from the constraints of both time and society.
Madness is further appealing because of the idea the consciousness demands coherence and form, both of which are ruined by changing time. It is therefore necessary to be mad in order to be conscious in this sense, because only through madness can you effectively stop time and formulate the necessary coherence and form. Henry IV has clearly done this by creating a role everything fits into a coherent historical period and where events are pre-formed.
Henry's revenge here is that when he wakes up out of his madness, he chooses to continue acting. This forces others to act with him; it his method of making the others go mad in order to humor him. By drawing people into his own world, Henry is able to exercise absolute power over them. He prefers this to the real world where shifting time means that there is never an absolute moment of control.
The arrival of Berthold is meant to provide the exposition for us. Notice that Berhold is used to call attention to the two large paintings. These paintings represent both the fixed and moving time, fixed in terms of the images they represent, but moving in terms of the fact that the people they represent are now older (notice that Henry IV has died his hair). "[The paintings] are images such as...well- such as a mirror might throw back." Thus the portraits are a way to see yourself caught in time. They make you younger and allow you to deny time. Henry IV is convinced the paintings are a magic trick of the Pope's; he wants to be free from always appearing at the same age.
The question of the real self emerges quite early in this act. Landolph tells Berthold: "We don't any of us know who we are really." He is alluding to the fact that they are all playing other roles, shown through the use of two separate names for each of them. This calls into question the real self, forcing us to realize that they are just as real when acting as counselors or when acting as valets.