Gabriel turned and walked over to St. Anne’s Gate, where a flock of nuns in gray habits was being admitted simply by saying “Annona,” the name of the Vatican supermarket. He tried the same tactic and, like the nuns, was waved onto Vatican territory. Just inside the gate he withdrew his Vatican ID badge and chastised the Swiss Guard in the Berlin-accented German he had acquired from his mother. Then he went back into the street. A moment later there came an elderly priest with very white hair who informed the Swiss Guard he was going to the Vatican pharmacy. The Guard detained the priest at the gate until he could produce ID from the pocket of his cassock.

Gabriel decided to check security at the other main entrance of the Vatican, the Arch of Bells. He arrived five minutes later, just in time to see a Curial cardinal and his two aides passing through the arch without so much as a glance from the Swiss Guard standing at attention near his weather shelter. Gabriel held his badge in front of the Guard’s eyes.

“Why didn’t you ask that cardinal for some identification?”

“His red hat and pectoral cross are his identification.”

“Not today,” Gabriel said. “Check everyone’s ID.”

He turned and walked along the outer edge of the Colonnade, pondering the scenes he had just witnessed. St. Peter’s Square, for all its vastness, was largely secure. But if there was a chink in the Vatican’s armor, it was the relatively large number of people who were allowed free movement behind the square. He thought of the photographs on Ali Massoudi’s computer and wondered whether the terrorists had discovered the very same thing.

HE CROSSED the square to the Bronze Doors. There were no magic words to gain admittance to what was essentially the front door of the Apostolic Palace. Gabriel’s badge was examined outside by a Swiss Guard in full dress uniform and a second time inside the foyer by a Guard in plain clothes. His Security Office clearance allowed him to enter the palace without signing in at the Permissions Desk, but he was required to surrender his firearm, which he did with a certain reluctance.

The marble steps of the Scala Regia rose before him, shimmering in the glow of the vast iron lamps. Gabriel climbed them to the Cortile di San Damaso and crossed the courtyard to the other side, where a waiting elevator bore him upward to the third floor. He paused briefly in the loggia to admire the Raphael fresco, then hurried along the wide corridor to the papal apartments. Donati, wearing a cassock with a magenta sash, was seated behind the desk in his small office adjacent to the Pope’s. Gabriel slipped inside and closed the door.

“How many people work inside the Vatican?” Donati said, repeating Gabriel’s question. “About half.”

Gabriel frowned.