THEY REACHED the Sala Clementina, a soaring frescoed receiving room one floor below the Pope’s private apartments, five minutes before the president. The Holy Father had not yet arrived. There was a detachment of ceremonial Swiss Guard standing outside the wide entranceway and several more in plainclothes waiting inside. Two ornate chairs stood at one end of the long rectangular room; at the other was a pack of reporters, photographers, and cameramen. Their collective mood was more disagreeable than usual. The equipment searches and security checks conducted by the Swiss Guard and Secret Service had been far more invasive than usual, and three European camera crews were refused entry because of minor discrepancies concerning their credentials. The press would be allowed to record the first moments of the historic meeting and broadcast the images live to the world, then they would be shepherded out.

Donati went back into the corridor to wait for the Holy Father. Gabriel looked around a moment longer, then went to the front of the room and positioned himself a few feet from the chair reserved for the Pope. For the next two minutes his eyes roamed over the pack of journalists, looking for any signs of agitation or a face that seemed in any way out of place. Then he did the same to the delegation of Curial prelates standing to his left.

Shortly before noon the white-cassocked figure of the Holy Father entered the room, accompanied by Donati, his cardinal secretary of state, and four plainclothes Swiss Guards. Erich Müller, the Guard who had given Gabriel his weapon, was among them. His eyes settled briefly on Gabriel, whom he acknowledged with a quick nod. The Pope walked the length of the room and stopped in front of his ornate chair. Donati, tall and striking in his tailored black cassock and magenta sash, stood at his master’s side. He looked briefly at Gabriel, then lifted his gaze toward the entranceway as the president of the United States strode through.

Gabriel quickly scrutinized the president’s official delegation. Four Secret Service agents were among them, he reckoned, maybe two or three more. Then his gaze began to sweep the room like a searchlight: the reporters, the Curial prelates, the Swiss Guards, the president and the Holy Father. They were shaking hands now, smiling warmly at each other in the blinding white light of the flashing cameras.

The swiftness of it caught even Gabriel by surprise. Indeed were it not for Donati, he thought later, he might never have seen it coming. Donati’s eyes widened suddenly, then he made a sudden lateral movement toward the president. Gabriel turned and saw the gun. The weapon was a SIG-Sauer 9mm—and the hand holding it belonged to Lance Corporal Erich Müller.