Below. Third level. The air conditioning makes a sound of sheet metal vibrating at the edges. It is eleven forty-two. The corridor is thirty-nine metres long, Reza Mahjoubi knows this because he counted the ceiling panels twice in his first week of service, four years ago.

The IAEA inspector walks half a step behind him. His name is Linde. Swedish, from Göteborg. His white shirt has a collar with a slightly curled edge. Reza notices things this way, one at a time. Linde carries a blue folder under his right arm and a small camera around his neck, grey plastic, IAEA sealed model.

The memorandum was signed in Geneva a week ago, on the 17th. Reza's superior, the engineer Karimi, had called him into the first-level office the next day. He had locked the door behind him, something he had never done. He had said: "you fill box three with the contents of box eight. You fill box four with the old contents of box three." Reza had answered: "I don't understand." Karimi had said: "you don't need to understand." He had left.

Reza had done as he was told. That evening he had called his wife, Sahar. He had told her only: "I had to do something at work that I don't understand." Sahar had said to him: "don't call me from work anymore, the siren's going, I'm off to fill the tub." They had hung up.

Reza, in the days that followed, had watched the news. They had said: international inspections, agreement, numbered boxes, declared material. He had understood something.

Now. Room B-12. Two boxes on the metal table, identical, forty centimetres high, thirty wide, white label with the number three, white label with the number four. Reza has two Yale keys on his belt. The right-hand key opens the three. The left-hand key opens the four. The keys are identical. Reza, in four years, has learned to tell them apart by touch: the right-hand one has a small crack on the side of the head, where he dropped it on the floor in his second week. The left-hand key is smooth.

Linde says in English: "open box three, please."

Reza says: "yes."

He knows. He knows that Karimi, from the third floor of the administrative building, is watching the camera. The camera is the one up on the right, a dark dome on the wall. He also knows that the right-hand key opens box three, that box three now holds the material moved last week from the eight, and that the material box three held before is now in the four.

He knows: if he opens the three, he shows Linde the material his superior wanted him to show. Linde takes the photograph, goes out, writes in the report that the Iranian declaration is consistent with the contents of box three. The superior is pleased. The country does not go back to being bombed. Sahar does not go back to filling the tub.

He knows: if he opens the four, he shows Linde the material the Iranian declaration at the table in Geneva set down. The IAEA report will tell the truth. Karimi will see it on the camera. Karimi will telephone security. Security will arrive within twenty minutes. Reza will not come home tonight.

He knows: his wife filled the tub three times last week.

Reza takes the right-hand key. He feels the small crack on the side of the head. He puts it into the lock of box three. He turns. He hears the click. He lifts the lid.

Linde bends down. He looks. He nods. He opens the blue folder, takes out a printed form, sets it on the table beside him. He compares the contents of the box with the list on the form. The codes, the quantities, the inner boxes with the seal. He nods again. He raises the camera. He frames the inside of the box. He takes three photographs: one from above, one from the corner, one of the register page fixed to the inner side of the lid.

Linde says: "thank you."

Reza says: "yes."

Linde waits. Reza closes the box again. He turns the key. He pulls the key out. He clips it back on his belt, the right-hand one on the right.

They leave room B-12. Reza escorts Linde to the lift. Linde, before stepping into the lift, shakes his hand. Reza returns the handshake. Linde's hands are dry. His are not.

Linde goes up. The lift door closes.

Reza goes back into the corridor. He stops in front of the internal telephone, on the wall. He lifts the receiver. He dials 3-1-1, which is the number of Karimi's office. He waits. Karimi does not answer.

Reza sets the receiver back on the hook. He stays standing in front of the telephone. He counts the ceiling panels, from the one above him to the lift. There are fourteen.

He thinks of Sahar. He thinks that at eleven forty-two in the morning she is probably in the bathroom, doing the housework, the radio on low. There is no siren at eleven forty-two. The sirens come at night.

Reza decides not to telephone her. He decides not to telephone anyone. He decides to go home at the usual time, seventeen thirty, by bus.

He leaves wing two. He greets the caretaker. The caretaker greets him. Reza goes up to the ground floor. He goes to the canteen. He eats rice with chicken. He drinks two glasses of water.

At seventeen thirty he is on the bus. At eighteen ten he is home. Sahar opens the door for him. She says to him: "are you tired?" He says: "no." She says: "I made the almond cake." He says: "good."

He sits down at the table. He eats. He does not tell her.