Meg and Sarah Altman (Jodie Foster and Kristen Stewert) have separated from Sarah’s father Stephen and are moving into a spacious three story brownstone apartment.
The unique thing about this house is the existence of a “panic room” adjoining the master bedroom on the second floor. The panic room is a ten foot by eight foot room, surrounded by concrete and steel. In it is a separate buried phone line, its own ventilation system, and a bank of security monitors covering the house.
Before going to bed on their first night in the house, Meg accidentally activates the security monitor. She vows to deactivate it first thing in the morning. She falls into a fitful sleep.
Director David Fincher then brings the camera down two stories where we see two burglars outside. One climbs up to the top of the house where he deactivates the alarm and lets himself in through a trap door in the ceiling of the third floor. This is Burnham (Forest Whitaker). As he walks back down to let his accomplice in, he notices Sarah sleeping in her bed. He also sees Meg asleep and by his reaction we know that he wasn’t expecting the house to be inhabited.
He goes down the stairs lets in Junior (Jared Leto). A man wearing a ski mask raps on the window. Junior motions him in. He is Raoul (Dwight Yoakam). Raoul and Burnham don’t know and don’t trust each other. Panicked, Burnham tells the other two about the occupants.
Burnham doesn’t like the idea of continuing the heist with Meg and Sarah in the house. After debate, they decide to go through with the plan. Junior is the grandson of the deceased former occupant of the house. He knows that inside the panic room is a safe containing a fortune. Burnham is the man who designed the panic room and can crack the safe. Raoul is along for muscle.
Raoul and Junior ascend the staircase to capture the two occupants and keep them quiet. But Meg is already is awake. After going to the bathroom, she returns to her room and notices the intruders on a monitor in the panic room.
She runs frightened to her daughter’s room on the third floor simultaneously alerting the burglars. They chase her. Meg wakes Sarah and throws them both in a small elevator. Raoul sees them get into the elevator and shouts to Junior that they’re coming down. On the second floor, Junior hits the call button to stop the elevator but it continues by him. He runs down the stairs after them, shouting to Burnham to stop them. Burnham says that he isn’t going to hurt anybody.
In the elevator, Sarah reminds her mom of the panic room. They lurch back to the second floor, jump out of the elevator, and dash into the panic room, closing the door just ahead of their pursuers.
The burglars panic. Burnham knows from experience that there is no way into the panic room. He also knows that the buried phone line in the panic room has not yet been activated.
Through written signs, the burglars tell Meg that what they want is inside the panic room. Burnham, Junior, and Raoul screw every door and window shut. Should Meg and Sarah get out of the panic room, they won’t be able to get out of the house.
Raoul and Junior start breaking a hole into the first floor ceiling with the idea of boring a hole through the bottom of the panic room. Burnham knows better. He finds a tank of propane gas and a hose outside. Systemically testing the wall, he finds the ventilation duct for the panic room. He drills a hole into the duct and runs the hose from the tank into the system. He lets a small stream of gas into the panic room but Raoul forces him aside and opens up the tank’s full force.
Meg smells the gas. She tells Sarah to stay low on the ground. She attempts to duct tape the vent shut. She finishes one but when she moves to the other, the first vent blows back open. Sarah jerks a cooler aside and finds a drainage pipe leading outside the house. They gasp for breath briefly. Meg tosses a fire blanket to Sarah and gets one out for herself. She pulls out a portable butane lighter and sets the propane on fire. She ducks beneath the blanket as the fire travels back through the duct down to the burglars below. Junior, who was holding his ear against the wall, is lit on fire. The tank whips around spewing flames as Raoul and Burnham extinguish Junior.
This briefly stumps the burglars. Sarah pulls out a small flashlight and begins coding SOS against the apartment across from the drainage pipe. A man gradually wakes up and sees the flashes but he goes to the window and closes the blinds.
Meg remembers a cell phone she left charging on the desk the night before. While the three burglars argue on the stairs, Meg opens the panic room doors and silently grabs for her cell phone. In the process she knocks over a lamp, alerting the burglars. Sarah and Meg manage to close the panic room door before the burglars get inside.
The cell phone gets no signal within the steel walls of the panic room. Meg gets the idea, however, of splicing the panic room’s phone into the house’s main phone line. Burnham hears her banging around in a crawl space looking for the main phone line. He runs to the basement to try to sever the line before she gets a call out.
Meg first calls 911 but they put her on hold. She then calls her husband but all she can get out is, “Stephen, there are three –” before Burnham smashes the phone line.
Here, we learn that Sarah has diabetes and is rapidly going into insulin shock. Meg now needs to get insulin for her daughter.
Frustrated and despairing, Junior tells the others that he is cutting his losses and leaving. As Junior leaves, Raoul pulls out a silenced pistol and shoots him twice in the head. Suddenly a voice pipes up. “What’s going on here?” It’s Stephen. Raoul shoves him to the ground, pulls out Stephen’s driver’s license and makes the connection that he is Meg’s husband.
On the security monitor, Meg and Sarah watch the burglars beat Stephen mercilessly. Burnham shouts at the camera for them to open the door but they don’t. They drag Stephen upstairs to the master bedroom and smash him some more. Burnham places his coat over the monitor in that room.
Next. On the monitor, Meg and Sarah see Burnham carrying what they think to be Raoul downstairs to the first floor. Meg opens the panic room door and sees on the bed what she assumes to be her husband.
She slinks down the stairs to her daughter’s room to try to acquire her insulin shots. While she’s gone, the man on the bed stirs and we see that it is Raoul. Burnham and Raoul enter the panic room and find Sarah in insulin shock. While Burnham inspects the panic room, Raoul shouts out the master bedroom to Meg, telling her to come let them finish things up. Meg creeps up to the door on the other side and slams it into his face. While he’s down, she makes a move for the panic room but stops short when she realizes that Burnham is inside. Raoul grabs her but she throws him into the wall and his gun goes flying. He scrambles into the panic room and Burnham hits the button to close the steel door. It slams right onto Raoul’s hand. He can’t pull it out and he writhes in pain. Burnham can’t open the door because Meg is holding Raoul’s gun on the door.
Through the door, Meg convinces Burnham to administer the insulin to her daughter. In return, Meg lets Raoul free his hand.
The cops arrive at the front door. Stephen had called them before he came over. Before she went to answer the door, Raoul had threatened Sarah’s life should Meg let cops in. The cops, although extremely smart, eventually take Meg’s word that everything is okay.
Now. Raoul, Burnham, and Sarah are in the panic room. Burnham cracks the safe and pulls out 22 million dollars in bearer bonds. Throughout all this, Meg is destroying all the security cameras in the house and breaking all the lights. She posts Stephen in front of the stairs with a gun and hides.
The burglars come out of the panic room. They’re holding Sarah as a shield. At the bottom of the stairs, the burglars and Stephen posture and bargain. They just want to leave but Stephen keeps them talking. Meg creeps out of an elevator behind them and slams Raoul in the face with a sledgehammer. He toppels over a railing. Burnham runs out a window.
Raoul, through a miraculous act of God or screenplay, is still alive. He drags himself up the stairs and attacks Meg. Burnham, at the street, hears the screams. His moral sense takes hold. He goes back and just as Raoul is about to bring the sledgehammer down on Meg’s head, Burnham shoots him.
The cops arrive and arrest Burnham.
At the end, Meg and Sarah look for a new home.