In the margin of his copy of Arithmetica, Pierre de Fermat had jotted the words I have a truly marvellous demonstration of this proposition which this margin is too narrow to contain.

The square had been converted to a cube, (x3 + y3 = z3), and mathematicians had spent centuries looking for the answer to Fermat's riddle. By the time Andrew Wiles solved the puzzle in the 1990s, he had been at it for ten years using the world's most advanced computer programme.

And all of a sudden she understood. The answer was so disarmingly simple. A game with numbers that lined up and then fell into place in a simple formula that was most similar to a rebus.

Fermat had no computer, of course, and Wiles' solution was based on mathematics that had not been invented when Fermat formulated his theorem. Fermat would never have been able to produce the proof that Wiles had presented. Fermat's solution was quite different.

She was so stunned that she had to sit down on a tree stump. She gazed straight ahead as she checked the equation.

So that's what he meant. No wonder mathematicians were tearing out their hair.

Then she giggled.

A philosopher would have had a better chance of solving this riddle.

She wished she could have known Fermat.

He was a cocky devil.

After a while she stood up and continued her approach through the trees. She kept the barn between her and the house.

CHAPTER 31

Thursday, April 7

Salander got into the barn through the outside hatch to an old manure drain. There were no livestock. She saw that the barn contained three cars - the white Volvo from Auto-Expert, an old Ford, and a somewhat newer Saab. Further in was a rusty harrow and other tools from the days when this had been a working farm.

She lingered in the darkness of the barn and watched the house. It was dusk and the lights were on in all the rooms on the ground floor. She couldn't see any movement, but she thought she saw the flickering glow of a television set. She glanced at her watch. 7:30. Time for Rapport.

She was surprised that Zalachenko would have chosen to live in such an isolated place. It was not like the man she remembered. She would never have expected to find him out in the country in a little white farmhouse. In some anonymous villa community, maybe, or in a vacation spot abroad. He must have made more enemies even than Salander herself. She was troubled that the place looked so undefended. But she had no doubt that he had weapons in the house.

After lingering for a long time, she slipped out of the barn into the twilight. She hurried across the yard, keeping her step light and her back to the facade of the house. Then she heard the faint sound of music. She walked noiselessly around the house and tried to peer through the windows, but they were too high.

Salander was instinctively uneasy. For the first half of her life she had lived in fear of the man inside that house. During the second half, ever since she had failed in her attempt to kill him, she had waited for the moment when he would come back into her life. This time she wasn't going to make any mistakes.

Zalachenko might be an old cripple, but he was a trained assassin who had survived on more than one field of battle. Besides, there was Ronald Niedermann to take into account. She would have much preferred to surprise Zalachenko outdoors, where he would be unprotected. She had no wish to talk to him and would have been satisfied with a rifle and a telescopic lens. But she had no rifle, and it was unlikely that he'd be taking an evening stroll. If she wanted to wait for a better opportunity, she would have to withdraw and spend the night in the woods. She had no sleeping bag, and even though the evening was mild, the night would be cold. Now that she had him within reach, she didn't want to risk letting him slip away again. She thought about Miriam Wu and about her mother.

She would have to get inside the house, but that was the worst possible scenario. Sure, she could knock on the door and fire her gun as soon as the door opened, and then go in to find the other bastard. But whoever was left would be alerted, and he would probably be armed. Time for a risk assessment. What were the options?

She caught sight of Niedermann's profile as he walked past a window only a few yards from her. He was saying something over his shoulder to someone.

Both of them were in the room to the left of the front door.

Salander made up her mind. She took the pistol out of her jacket pocket, clicked off the safety, and moved silently onto the porch. She held the gun in her left hand as she pressed the front door handle down with excruciating caution. It was unlocked. She frowned and hesitated. The door had double dead bolts.

Zalachenko should not have left the door unlocked. It was giving her goose bumps on the back of her neck.

It felt wrong.

The hallway was black as pitch. To the right she glimpsed the stairs to the upper floor. There were two doors straight ahead and one to the left. Light was seeping through a crack above the door. She stood still and listened. Then she heard a voice and the scraping of a chair in the room to the left.

She took two swift steps and threw open the door and aimed her gun at...  the room was empty.

She heard the rustle of clothing behind her and spun around like a lizard. As she tried to raise the gun to firing position, one of Niedermann's enormous hands closed like an iron vise around her neck and the other clamped around her gun hand. He held her by the neck and lifted her straight up in the air as if she were a doll.

For a moment she kicked her feet in midair. Then she twisted around and kicked at Niedermann's crotch. She hit his hip instead. It felt like kicking a tree trunk. Her vision was going black as he squeezed her neck and she felt herself drop the gun.

Fuckers.

Then Niedermann threw her across the room. She landed on a sofa with a crash and slid to the floor. She felt blood rushing to her head and staggered to her feet. She saw a heavy glass ashtray on a table and grabbed it and tried to fling it backhand. Niedermann caught her arm in mid-swing. She reached into her left pants pocket with her free hand and pulled out the Taser, twisting around to shove it into Niedermann's crotch.

She felt a hefty jolt from the electric shock come through the arm Niedermann was holding her with. She had expected him to collapse in pain. Instead he looked down at her with a surprised expression. Salander's eyes widened in alarm. He seemed to experience some unpleasantness, but if he felt any pain he ignored it. This man is not normal.

Niedermann bent and took the Taser from her and examined it with a puzzled look. Then he slapped her across the head. It was like being hit with a club. She tumbled to the floor next to the sofa. She looked up and saw that Niedermann was watching her curiously, as if wondering what her next move would be. Like a cat getting ready to play with its prey.

Then she sensed a movement in the doorway. She turned her head.

He came slowly into the light.

He was leaning on a forearm crutch and she could see a prosthesis sticking out from his pants leg. There were two fingers missing from his left hand.

She raised her eyes to his face. The left half was a patchwork of scar tissue. His ear was a little stump and he had no eyebrows. He was bald. She remembered him as a virile and athletic man with wavy black hair. Now he was about five foot four, and emaciated.

"Hello, Pappa," she said tonelessly.

Alexander Zalachenko regarded his daughter without expression.

Niedermann turned on the ceiling light. He checked that she had no more weapons by running his hands over her clothes and then clicked the safety on the P-83 Wanad and released the magazine. Zalachenko shuffled past them, sat in an armchair, and picked up a remote control.

Salander's eyes fell on the TV behind him. Zalachenko pressed the remote, and she saw a green flickering image of the area behind the barn and part of the driveway to the house. Infrared camera. They had known she was coming.

"I was beginning to think that you wouldn't dare to make an approach," Zalachenko said. "We've been watching you since 4:00. You tripped just about every alarm around the farm."

"Motion detectors," Salander said.

"Two by the road and four in the clearing on the other side of the field. You set up your observation post on precisely the spot where we'd positioned alarms. It's the best view of the farm. Usually it's moose or deer, and sometimes berry-pickers who come too close. But we don't often get to see somebody sneak up to the front door with a gun in their hand." He paused for a moment. "Did you really think Zalachenko would sit in his little house in the country completely unprotected?"

Salander massaged the back of her neck and began to get up.

"Stay there on the floor," Zalachenko said.

Niedermann stopped fiddling with the gun and watched her quietly. He raised an eyebrow and smiled at her. Salander remembered Paolo Roberto's battered face on TV and decided it would be a good idea to stay on the floor. She breathed out and leaned back against the sofa.

Zalachenko held out his intact right hand. Niedermann pulled a weapon out of his waistband, cocked it, and gave it to him. Salander noticed that it was a Sig Sauer, standard police issue. Zalachenko nodded, and Niedermann turned away and put on a jacket. He left the room and Salander heard the front door open and close.

"In case you get any stupid ideas, if you even try to get up I'll shoot you right in the gut."

Salander relaxed. He might manage to get off two, maybe three shots before she could reach him, and he was probably using ammo that would make her bleed to death in a few minutes.

"You look like shit," Zalachenko said. "Like a fucking whore. But you've got my eyes."

"Does it hurt?" she asked, nodding at his prosthesis.

Zalachenko looked at her for a long time. "No. Not anymore."

Salander stared at him.

"You'd really like to kill me, wouldn't you?" he said.

She said nothing. He laughed.

"I've thought about you over the years. In fact almost every time I look in the mirror."

"You should have left my mother alone."

"Your mother was a whore."

Salander's eyes turned black as coal. "She was no whore. She worked as a cashier in a supermarket and tried to make ends meet."

Zalachenko laughed again. "You can have whatever fantasies you want about her. But I know that she was a whore. And she made sure to get pregnant right away and then tried to get me to marry her. As if I'd marry a whore."

Salander looked down the barrel of the gun and hoped he would relax his concentration for an instant.

"The firebomb was sneaky. I hated you for that. But in time it didn't matter. You weren't worth the energy. If you'd only let things be."

"Bullshit. Bjurman asked you to fix me."

"That was another thing entirely. He needed a film that you have, so I made a little business deal."

"And you thought I'd give the film to you."

"Yes, my dear daughter. I'm convinced that you would have. You have no idea how cooperative people can be when Ronald asks for something. And especially when he starts up a chain saw and saws off one of your feet. In this case it would have been appropriate compensation - a foot for a foot."

Salander thought about Miriam at the hands of Niedermann in the warehouse. Zalachenko misinterpreted her expression.

"You don't have to worry. We don't intend to cut you up. But tell me: did Bjurman rape you?"

She said nothing.

"Damn, what appalling taste he must have had. I read in the paper that you're some sort of fucking dyke. That's no surprise. There can't be a man who'd want you."

Salander still said nothing.

"Maybe I should ask Niedermann to screw you. You look as if you need it." He thought about it. "Although Ronald doesn't have sex with girls. He's not a fairy. He just doesn't have sex."

"Then maybe you should screw me," Salander said to provoke him.

Come closer. Make a mistake.

"No, thanks all the same. That would be perverse."

They were silent for a moment.

"What are we waiting for?" Salander asked.

"My companion is coming right back. He just had to move his car and run a little errand. Where's your sister?"

Salander shrugged.

"Answer me."

"I don't know and I honestly don't give a shit."

He laughed again. "Sisterly love, eh? Camilla was always the one with the brains - you were just worthless filth. But I have to admit it's quite satisfying to see you again up close."

"Zalachenko," she said, "you're a tiresome fuck. Was it Niedermann who shot Bjurman?"

"Naturally. Ronald is the perfect soldier. He not only obeys orders, he also takes his own initiative when necessary."

"Where did you dig him up?"

Zalachenko gave his daughter a peculiar look. He opened his mouth as if to say something, but decided against it. He glanced at the front door and then smiled at Salander.

"You mean you haven't worked it out yet?" he said. "According to Bjurman you're supposed to be a good researcher." Then Zalachenko roared with laughter. "We used to hang out together in Spain in the early nineties when I was convalescing from your little firebomb. He was twenty-two and became my arms and legs. He isn't an employee...  it's a partnership. We have a flourishing business."

"Sex trafficking."

"You could say that we've diversified and deal with many different goods and services. Our business model is to stay in the background and never be seen. But you must have worked out who Ronald is."

Salander did not know what he was getting at.

"He's your brother," Zalachenko said.

"No," Salander said, breathless.

Zalachenko laughed again. But the barrel of the pistol was still pointed unnervingly at her.