IT HAD BEEN SERGIO MOZZICARELLI’S SHIFT IN THE INFIRMARY. He’d been sent out to bring a meal to Omar Ben Taleb, the Tunisian who’d been beaten badly a few days earlier by the Professor and his friends. He made his way through the armored doors that the guards opened for him, one by one, without a word of greeting. It wasn’t that they had any bad feelings about him, either way; it was just that they couldn’t remember his name, in spite of the fact that Mozzicarelli had been an inmate of that house of detention for seven long years. Sergio was an invisible man. A face in the crowd, of ordinary height and stature, an undistinguished gaze. He was a fleeting shadow, a breath of wind. In the past, this quality had come in handy when he wanted to hide or avoid arousing suspicion. And even in prison, never being at the center of attention was, all things considered, a distinct advantage. Being an anonymous character, a mere cameo in the lives of others, had come naturally to him. He was at his ease in that transparent body that no one ever took aim at, of which no one ever asked a favor. But now, he thought, that very same transparency was dragging him into real trouble because it had allowed him to see everything, to know everything. Shadows don’t have consciences, he kept telling himself, but somehow he couldn’t master that anxiety; he couldn’t manage to keep to himself the nugget of information that could pin down a killer, bring him to justice. He got to the last barred gate, the one that gave onto the infirmary ward. Officer Tolotta, tall and imposing, smiled as he opened the door for him. This guard, like all the others, couldn’t remember his name. “Is this for Omar? Let me take a look.” He studied the tray. Next to the bowl of minestrone was a slice of light-colored meat. “What is it?”

“I don’t know . . . beef . . . pork.”

“Pork? Have they lost their minds in the kitchen? He can’t eat pork. Well, anyway . . . you tell him that it’s beef . . .”

Sergio smiled as Federico Tolotta snapped the lock open.

The only patient in the six-bed ward of the infirmary was Omar. Mozzicarelli walked over to him. The young man lay there with his eyes shut. His face was swollen. His lips were split, his nose was bandaged, and he had two black eyes. One hand was wrapped in gauze dressings. In the other arm was a needle and an IV tube.

“Time to eat!” said Sergio. He set the tray down on the nightstand. “Are you strong enough, or do you need me to call a nurse for you?”

Omar barely opened an eye. He looked at the other inmate. “Sergio . . . you’re Sergio, right?” he said.

Sergio was astonished. “Yes, that’s me. Why?”