Now he understood. An overdose of insulin, given to a sleeping patient, would swiftly induce hypoglycemic coma as the neurons in the brain were starved of glucose. Death would follow if the condition was left untreated, and if the injection site itself were not spotted, there’d be no reason to suspect foul play. Insulin was one of the most effective murder weapons a hospital could offer.

Carver had no intention of being its latest victim. He came up behind the intruder, slipped the bathrobe cord over his head, and pulled it tight around the neck.

The man reacted instantly. He brought his left hand up to the cord, trying to pull it away from his throat. At the same time he jerked his head back, hard, hoping to catch Carver on the face.

Carver anticipated the move and swayed back, his own movement adding to the tension on the cord. But now he had another problem to deal with-the man swung his right arm around behind him, jabbing the injector pen at Carver like a deadly snake, with insulin as its venom.

Carver twisted to one side to avoid the pen. The movement shifted his balance and gave his opponent the chance to push backward. Carver was sent crashing into the wall between his room and the one next door. The breath was knocked from him by the impact, but he forced himself to hold on to the cord. Ten or fifteen seconds’ pressure on the carotid artery would be enough to bring on unconsciousness, but fifteen seconds was an eternity when two men were fighting to the death.

They lurched around the room, their bodies linked like two drunken dance partners as they collided with a chair, knocking it over; then the bed; then a side table, sending a glass of water flying. And all the while the injector was jabbing at Carver, searching for his flesh and the moment when it could finally release its deadly cargo.

Groggy calls of complaint started coming from the patients on either side of Carver’s room. One of them started banging on the wall and calling for a nurse. It would not be long before someone came to see what was happening.

As the seconds passed, the fight was becoming a test of endurance between Carver’s enfeebled muscles, desperately hanging on to his improvised noose, and his enemy’s oxygen-starved brain. Whoever gave in first would die. And then came a stroke of luck. The assassin’s flailing hand struck against the iron frame of Carver’s bed and the injector was knocked from his grasp. Desperately, he tried to bend down to pick it up, but that only gave Carver the opportunity to plant his feet and give one last heave of the cord.

He felt the other man slump into unconsciousness and let the cord play out through his hands, lowering the lifeless body to the floor.

Suddenly there was a hammering on the door.

Carver dragged the body into the bathroom, then opened the door. Christophe, the crack-addicted son of a prominent local banker, was standing in the corridor in shorts and an old T-shirt, his usually pallid features inflamed with indignation.

“What the hell have you been doing in there?” he whined, making no attempt to keep his voice down.

Other heads began peering out of doors up and down the corridor.

“It’s okay-I’m sorry,” said Carver, turning to one side and then the other, holding his hands up in apology and surrender.

“I must have been sleepwalking or something. I had one of my nightmares, then I woke up and I was in the middle of my room and it was all smashed up. I don’t know what happened. But I’m really sorry if I woke you guys up, okay?”

He looked around in feigned bewilderment. “Has anyone seen a nurse? I could really use some meds…”

The others shook their heads and retreated back into their rooms, like crabs scuttling back into holes, not wanting to get involved. Carver watched them disappear, then went back into his room. Wherever the nurse had got to, she’d be back at any second. He heard a groan from the bathroom. His assailant was coming to.

Carver’s eyes darted around his room until he found the injector lying on the floor by his bed. He picked it up, strode into the bathroom, sat astride the man’s body, forced his head down with one hand, then jabbed the injector at his carotid artery with the other. As soon as the plastic tube hit skin, Carver pushed the trigger button, sending a dose of insulin straight into the bloodstream. Then he pressed it again, twice more, just to make sure the maximum possible dose had been administered and the injector was completely empty. The man gave a barely audible moan. He wasn’t dead yet. But he was heading that way fast.

Now that the fight was over and his adrenaline levels were plummeting, Carver felt shattered, but he couldn’t afford to let up. He righted the bedside table and put the chair back in its place. Somehow, he found the strength to drag the comatose body back out of the bathroom and across the floor to the bed.

The man had been wearing a heavy overcoat. Carver pulled his arms from the sleeves, then heaved him up onto the mattress and covered him with a blanket and top sheet, leaving just the top of his head exposed on the pillow. The subterfuge would survive only the most cursory look into the room. But it might buy Carver time to get out.

He put on some clothes and shoes, followed by the dying man’s overcoat. There were car keys in one of the side pockets, along with a phone. The inside pocket held a wallet. Carver opened it. He found money, credit cards, and an I.D. in the name of Dr. Jean Du Cann, consultant psychiatrist. That would have got the would-be killer past the guard at the gate. He must have used it again at the front desk or slipped in through a service entrance. Those doors were all locked, but they wouldn’t pose any barrier to a professional. They wouldn’t stop Carver getting out, either.

He was about to leave the room when he heard more footsteps: the slightly sharper patter of a nurse’s footsteps. Sandrine had returned. There was a distinct, familiar pattern to the noise she was making: a few paces, then a pause as she looked into the patients’ rooms, through the windows in the doors, just a routine check to make sure they were all okay.

Carver rolled under the bed as her footsteps drew near. He held his breath and remained perfectly still as she stopped outside his room, then exhaled in blessed relief as she walked on. A couple of minutes later, he heard one last, uninterrupted walk down the corridor, followed by the sound of the TV being turned on again. He waited a few minutes, giving the nurse time to fix herself a cup of coffee, kick off her shoes, and relax in front of the box.

He used the time to sort out the dying man’s possessions. Carver kept the coat, the phone, the car keys, and the cash. The wallet, with the doctor’s I.D. still inside, he placed on the bedside table, along with the injector. That would give the police plenty of material to go on when they tried to figure out what had happened-material that should make it obvious that the victim was far from innocent. Finally, Carver slipped out through his door, turned away from the nurses’ room, crept down the corridor, and made his way to the emergency staircase.

Less than a minute later, he was sitting behind the wheel of his attacker’s car. He turned up the collar of his overcoat, then drove toward the barrier, giving the guard a little wave of thanks as he passed. As the barrier closed behind him, he pressed the accelerator to the floor and sped away toward Geneva.

At a quarter past midnight, Clément Marchand came through his front door, an eager, expectant look on his face. “Marianne? Chérie? ” he called out.

Then blood blossomed on his shirt front and spattered his forehead as he died just as his wife had.

The killer let himself out of the apartment without any fuss. As he drove away he called his boss, reporting the situation at the apartment and requesting his next instructions.