The film begins in Warsaw, Poland, in August 1939. Everything is normal until Hitler appears in Warsaw, and then everyone stops to stare. The people try to figure out how he got here and whether his appetite has grown to desire Poland as well.

A young boy, Wilhelm Gustev, comes to ask for a tank that he was promised for a good report card. The man asks the boy whether he will show it to his father and tell him that Hitler gave it to him so that his father will like him better. Then the boy says that his father doesn't like Hitler at all, upon which Hitler enters and says, "Heil myself."

Suddenly, the director begins to yell at everyone to stop the performance. He doesn't want the play to become funny since he wants it to be a very serious documentary on Hitler and the concentration camps. The man says that he looks like Hitler, but the director disagrees. So, he walks out into the street, and we discover that this is how Hitler came to Warsaw in 1939.

Next we see that the stars of the last show, Joseph and Maria Tura, are now performing in Hamlet. Joseph and Maria talk, and Joseph tries to convince her that he truly loves her. When he walks into her room, he becomes insanely jealous when he sees that she has received flowers from an unidentified admirer for the third night in a row.

After Joseph leaves, Maria tells her maid that she is certain they're from a handsome aviator. She reassures the woman that she loves her husband, but he becomes upset by such little things. A man later arrives with a note from the handsome aviator, and she decides to see him later. She writes back to the man that he should come to her dressing room during Hamlet's soliloquy that begins with "To Be or Not To Be." As the speech begins to speak, the handsome young aviator gets up and heads to Maria's dressing room.

When he comes in, Maria invites him to sit and talk to her. She thanks him for the flowers, and he tells her that he's seen her in everything she's ever performed in. The man begins to question her based on her interviews, and she has no idea what he's talking about since she often lies during them.

After they talk for a few moments, the aviator asks Maria to see his plane, and she agrees to meet him at the airport the next day. Maria reminds the maid not to tell her husband. Later Joseph comes to her room and shares his disappointment about someone walking out during his performance. She convinces him that the man was probably about to die unless he left.

As they prepare for the next play, Joseph and Maria listen to the radio and hear that Hitler is speaking. Some men from the war office then come in to tell them that they will not be able to open the show that night, because it's not safe. They are angry about the order, but they decide to perform Hamlet again anyway. As Stanislav, the aviator, leaves during the soliloquy again, Joseph becomes infuriated.

In the back, Stanislav tells Maria that they must tell her husband that they love each other. Stanislav also tells her that she will no longer have to work. He plans to tell her husband, but Maria says that she loves her husband. A moment later, her maid runs in and announces that the Germans have entered Poland with no formal declaration of war. Stanislav tells her goodbye, and she asks him to come back. He says that he must in order to see her again.

As everyone runs backstage, the sirens begin, and people rush out of the theater. They hide downstairs as Warsaw is bombed. When the bombing is over, we see that most of the town as we saw it in the beginning is destroyed. Nazi soldiers march through the streets as people look on over the rubble. Curfews, trips to the concentration camp, and death penalties are enacted in the city.

A new spirit comes over the people as they begin to hate Hitler. Around the city, people put up "V"'s for victory. The fight for freedom comes out of England as young Polish men of the R.A.F. try to win freedom for their home country. They gather together and sing about beating Hitler.

Professor Siletsky tells the men that he will be discontinuing his radio speeches in order to go on a secret mission. He reveals that he is going to Warsaw, and the men of the R.A.F. discuss how terribly they want to go back. He agrees to try his best to find out about their families. Stanislav asks the Professor to find Maria and tell her, "To Be or Not To Be." Stanislav is shocked that Siletsky doesn't know who Maria is.

Stanislav goes to some of the leaders of the military and tells them that he suspects Siletsky is lying about his identity. He believes that since Siletsky did not know who Maria Tura was, he must be lying as she is the most famous actress in Warsaw. The leaders tell him that there is no reason to be concerned, but they are disturbed that he told the men where he was going. They are shocked that he took the names since they could easily fall into the hands of the Gestapo. The men discuss how the underground in Warsaw could be destroyed if Siletsky is a traitor. They tell Stanislav to go to Warsaw so that he can warn the underground.

Stanislav parachutes from his plane and runs from the Gestapo who see him fall. He finally escapes and hides from them. Inside the bookshop, Maria asks for the book that Stanislav was told to ask about, Anna Karenina, and places something on page 105 just as Stanislav was instructed. The bookkeeper hurries to the back and finds Siletsky's picture with a note on the back that he must not reach the Gestapo. Soon after, two soldiers go to Joseph and Maria Tura's apartment, and they ring the doorbell as she arrives there. The men take her with them as Stanislav sleeps inside.

Inside the Nazi headquarters, Maria meets with Professor Siletsky. She is obviously nervous, and he offers her a cigarette. He apologizes for bringing her in that way, and he gives her the message from Stanislav. His phone suddenly rings, and he makes an appointment for meeting with the Gestapo the next morning. Siletsky warns her that she should be careful to choose the right side. He asks her to be a spy for the Germans and offers to make her life more comfortable. Siletsky tries to explain that the Nazis are just trying to create a happy world. He says he is not a monster, and he asks her to remain for dinner and the rest of the evening. Siletsky then allows her to leave, and she hurries home.

Joseph arrives home and finds Stanislav asleep in his bed. When he says, "To Be or Not To Be," Stanislav gets out of bed. Maria runs in and tells them that Siletsky is in town but hasn't talked to the Gestapo yet. Joseph wants to know what's going on, and she tells him that she has to have dinner with Siletsky and may possibly kill him. Joseph tells her that he'll take care of things by killing Siletsky himself.

Maria arrives at Siletsky's hotel room in a beautiful dress. They drink together, and she admits that she's scared of him. She asks him to write his name so that she can tell him everything about himself. She tells him that he is a very determined and charming man. Then, he kisses her, and she says, "Heil Hitler." Suddenly someone knocks at the door, and he escorts her into the other room so he can consult with someone. He is told that he must see Colonel Ehrhardt immediately. She watches, disturbed, as he takes out the papers with the names of the men's families and friends on it and leaves.

Maria takes the page where he signed his name and begins to type on it. She types, "My nerves are cracking. My life is of no use to the Fuehrer any more. I am going to end it. Heil Hitler!" Then she slips it under his pillow. After leaving the note, she tries to leave, but since he left no instructions she is trapped.

At the theater, the men arrange a fake Gestapo headquarters. Siletsky arrives and meets with Joseph who is disguised as Colonel Ehrhardt. The first general he meets laughs a lot, but a soldier reassures him that he only became a general due to a relationship with a high-ranking official. They then let Siletsky in to meet with Ehrhardt. Siletsky tells him that in England, he is known as "Concentration Camp Ehrhardt." Siletsky tells him that he will send the duplicates the next morning. Joseph is disturbed by this news, and he realizes that they can't kill him now.

Joseph tries to talk to Siletsky, but he just stumbles across his words. The other men hiding off stage give him a plan, and then he talks to Siletsky about Maria. He reveals that Stanislav sent a message to Maria through Siletsky. When Joseph hears the message, he becomes very angry. Siletsky finally realizes who Joseph is, and he holds him at gunpoint. Siletsky runs and hides in the theater. Finally, they catch him, shoot him, and then he falls to the ground, dead.

At the hotel, a man comes to the room looking for Siletsky. The man decides to wait for Siletsky to return. Later, Joseph returns to the room disguised as Siletsky. The man is a worker for Ehrhardt, and Joseph tells him all about the message from Stanislav. The man tells him that the colonel is expecting him immediately. Joseph and Maria walk into the other room to get the papers out of the trunk. Joseph begs her to tell him about Stanislav. She encourages him that he is a great actor, and he can perform well before Ehrhardt.

Ehrhardt tells Joseph that his good friend, Hitler, is coming into town the next day. He tells him that he is called Concentration Camp Ehrhardt in London. Ehrhardt asks for the information and about his plans for the underground movement. Joseph gives him the name of the leader, and when the soldier enters, he says that the man was killed several days earlier. The other man who was a good possibility was killed too. Joseph tells Ehrhardt to book him two flights back to England so that he can take Mrs. Tura back as a spy as well.

Maria meets with Ehrhardt a few days later, and she is shocked to hear that Siletsky was murdered. They were planning to do a show in the theater when they found his body. Ehrhardt offers to get to know her better and allow her continue being a spy. Suddenly, Ehrhardt's phone rings, and Siletsky is on the line. Maria hurries to try to meet with Joseph, but he has already left. Then she returns home to find Stanislav there; he saw Joseph when he came in and punched him in the jaw, but then Joseph left. She also runs to the theater, but she just misses Joseph again.

Joseph then comes in to meet with Ehrhardt. He is introduced to some people from the Special Investigations squad, and then he is brought into another room to meet with Ehrhardt. Joseph sits down before he realizes that the dead Siletsky is sitting in a chair. He goes to the bathroom and finds a razor. They are leaving him inside until he cracks.

However, Joseph comes to the door and tells the squad that their friend is dead. Ehrhardt tells him that he believes that he is the imposter. Schultz accuses him of tailing Siletsky for several months to grow such a beard. Ehrhardt tries to convince Joseph to pull off Siletsky's beard, but then Ehrhardt does it and finds that the beard is false. They decide that Siletsky should leave immediately with Maria. Another man walks inside, exclaiming that they have found a plot against Hitler. He then pulls Joseph's beard and shows that it's a fake. Ehrhardt quickly discovers that he will be losing his job. The men, however, are actually part of the underground.

Back at the meeting place, everyone talks about what to do to protect the cause. They decide to cause a commotion and confuse the Gestapo so that they'll leave Hitler's box. Both Joseph and Stanislav take their leave of Maria and go to the theater. The Gestapo goes into the theater while the men of the underground dressed as soldiers enter the Gentleman's Lounge. Then, Hitler arrives and the commotion begins.

Suddenly, one of the actors appears, and then the soldiers grab him. The rest of the underground also comes over so that they can save him. He is taken away for questioning, and Joseph says that he doesn't want to hear anymore about this event. He then advises Hitler to leave immediately, and the soldiers follow. Joseph and the other actor playing Hitler step into the car and leave the theater.

It is then that Joseph and the actor hear an explosion, and they realize that the underground is still alive. Joseph realizes that he has lost his mustache, but they realize that he can't get out of the car without it. Ehrhardt and Shultz show up at Maria's apartment, and she tries to throw them off track. Ehrhardt refuses to leave, however, and she tries to avoid his advances. The man playing Hitler hurries upstairs to meet her, and Ehrhardt is terrified that he has made a mistake when he realizes that she is having an affair with Hitler. Ehrhardt then shoots himself in her apartment.

On the plane, the pilots are asked to meet with Hitler himself while Stanislav takes over the controls. He tells them to jump out of the plane, and they do so immediately. Finally, everyone parachutes from the plane, and they arrive in England. Joseph's greatest desire is to play Hamlet. He is then shown playing his favorite part, and he watches in shock as Stanislav once again gets up at the start of the soliloquy.