She was carrying a pound of high explosives in her Macy’s shopping bag.

The hallway on the penthouse floor was surprisingly short. Aminah pressed the buzzer next to the door labeled A—and the door opened immediately.

She was met by a Saudi Arabian with handsome features offset by a nickel-size mole on the left edge of his jaw. His black eyes judged her.

For his part, Baada Bin-Hezam, when he first saw the red-faced, stocky woman, thought for an instant that she was the hotel maid. Then he saw the shopping bag in her hand. She was not what he imagined when he was informed that he would be contacting a sleeper agent in the United States. This American woman held very little intrigue.

There were no passwords for this meeting. Bin-Hezam stepped aside so that she could enter, then closed the door, locking it behind her.

Aminah walked a few paces forward, then stopped. She had not been alone in a room with a man for a long time. She felt even more uncomfortable because of the way she was dressed. Compared to her usual attire, even the most modest of Western clothes drew attention to the feminine figure.

She glanced at his face again and saw that his thick-lidded eyes were downcast, avoiding her face and her body out of respect. This was a source of relief to her.

“Assalamu alaikum,” he said.

She did not know whether to continue into the main room or await instructions. “Walaikum assalam,” she said.

“Please,” Bin-Hezam said, stepping into the room. He reached out his hand to take the shopping bag from her. Then he introduced himself formally. “I am Baada Bin-Hezam.”

“I am Aminah bint Mohammed. Please forgive my presence, and . . .” She did not know how else to say it. She knew he had been expecting a man. She had heard it in his voice on the telephone. She wanted somehow to apologize, not for her gender, but for the awkwardness posed by her presence.

He moved around her into the sitting room. The room assaulted Aminah’s eyes with its insistent decor even in the dimness of the light from a single floor lamp and the overhead globe in the entry hall. The drapes were closed, a bright sliver of afternoon sun slashing into the room through the narrow gap where they did not quite meet.

It was indeed a setting for illicit behavior, though not of the kind normally associated with hotel rooms.

On a small, round dining table, she saw two black messenger bags, a large plastic bag of folded white gauze, a small blue box, a curled sheet of plastic, and some things that looked electronic. Through the open door into another room, she saw a bed on which the jacket and trousers of a coffee-brown suit and a folded white shirt were neatly laid out as though in a vestry.

“Sit,” said Bin-Hezam, motioning Aminah to one of two purple horseshoe chairs. He removed the sweater from the shopping bag and set it aside, carefully taking out the twin plastic-wrapped loaves of explosives and placing them on the tabletop.

With the tenderness of a man unwrapping a swaddled newborn, he opened one of them. He touched it to test its consistency. It held the impression of his finger when he pushed down. The fresh explosive was as malleable as plumber’s putty.

“Yes, you have done well,” Bin-Hezam said to Aminah.

Her spirit lifted. “I followed instructions. It is good?”

“Very good.”

She wanted only to be useful. God had seen fit that she should be adequate to the challenge today. This feeling would raise her up and carry her through the rest of the day.

He studied the fingerprint impression he had left in the explosive. Each half-pound loaf was powerful enough to turn a three-bedroom suburban house into a pile of splinters. The blast would kill anyone within a radius of fifty yards and maim out to a hundred yards. Ignited in an open field, it would yield a crater thirty feet in diameter and ten feet deep.

Bin-Hezam gingerly rewrapped the loaf with his fingerprint on it, sliding it into one of the black messenger bags, which he then set apart from the rest of the items on the table.

He put the other slab carefully into the second messenger bag, followed by the gallon-size bag of white gauze, a box of cotton, the plastic sheeting, the model rocket fuel pellets, and the electronic ignition components. Bin-Hezam hefted the bag gently to let everything settle, then checked the interior again to confirm that he had packed it well enough to prevent accidental explosion. Unlikely, but possible. All told, the messenger bag with its contents weighed about five pounds.

“This is for you,” he told her.

She was surprised to carry only one. But she did not question his command.

“These things I give you are very important. You have provided the most critical element of all.”

Bin-Hezam took a breath. His most crucial task was the instructions he was about to give her. Everything hinged on this American woman now.

“You will take this bag by taxicab to the East Eighty-fifth Street entrance of the Central Park. From there, you will walk into the park to the south end of the reservoir. There you will find a granite pump house. You will wait outside until you are greeted. Is that clear? Until you are greeted.”

“Will it be a man?” she asked.

Bin-Hezam hesitated before answering. “It is best that you do not know.”

“How will I know it is . . . the person?”

“They will find you there and summon you. You will know them the way you would know Allah. And then you will follow their instructions. You may have to wait some time for the meeting. Maybe hours. You will be patient?”

Aminah nodded sincerely.

“Perhaps you should bring a book—a Western book—in order to appear leisurely and occupied. Your contact will have very little time, so it is critical that you are available.”

Aminah felt certain it was to be a man. She believed that Bin-Hezam would have told her if it was a woman, knowing that it would have a calming effect on her.

“First a hotel room, then a rendezvous in the park,” she said. “After years of strict observance, I am disobedient at the end.”

She was making a joke, but also telling the truth. For the first time since the door opened she looked directly into Bin-Hezam’s eyes.

He nodded paternally. He accepted her. That much was enough.

He said, “You have never been more observant than you are today.”

“Please forgive me, but . . . can you tell me what it is we will achieve?” she asked.

“This is a perfect plan because none of us except for the last person knows what is to come.”

Aminah nodded, then lowered her head. “Insha’Allah,” she said.

Bin-Hezam said, “There is no reason for you to delay.”

“I have one request,” she said, her heart starting to race.

Bin-Hezam looked at her doubtfully. “What is it?”

“May we pray together before I go? Is it allowed in the same room?”

Bin-Hezam appeared warmed by this display of devotion. “It is allowed.” He stretched out his arm, pointing to indicate the east. “You must kneel behind me, that is all.”

He left the room, returning a moment later with his prayer rug and a bath mat for Aminah. Together, they moved two chairs aside to give them room.

“Do you know the passage?” Aminah said.

“I memorized it as a boy,” Bin-Hezam answered. “As a child, when this great day was only a dream.”

“I am grateful to you, Baada Bin-Hezam,” she said. Aminah closed her eyes and waited for God to flow into her as Bin-Hezam prayed aloud.

“Think not of those who are slain in Allah’s way as dead,” he intoned in a soft, lilting Arabic that was almost a song, his hands open to heaven, his eyes closed. “Nay, they live, finding their sustenance in the presence of their Lord. They rejoice in the bounty provided by Allah. By Him in whose hands my life is! I would love to be martyred in Allah’s cause and then get resurrected and then get martyred, and then get resurrected again and then get martyred and then get resurrected again and then get martyred.”