So, the gendarme thought, the rumors were true. Gabriel Allon, renowned restorer of Old Master paintings, retired Israeli spy and assassin, and savior of the Holy Father, had returned to the Vatican. With a single keystroke, the officer cleared the file from the screen. Then he made the sign of the cross and for the first time in many years recited the act of contrition. It was an odd choice, he thought, because he was guilty of no sin other than curiosity. But surely that was to be forgiven. After all, it wasn’t every day a lowly Vatican policeman had the chance to gaze into the face of a legend.

Fluorescent lights, dimmed to their night settings, hummed softly as Gabriel entered the main conservation lab of the Vatican Picture Gallery. As usual, he was the first to arrive. He closed the door and waited for the reassuring thud of the automatic locks, then made his way along a row of storage cabinets toward the floor-to-ceiling black curtains at the far end of the room. A small sign warned the area beyond the curtains was strictly off-limits. After slipping through the breach, Gabriel went immediately to his trolley and carefully examined the disposition of his supplies. His containers of pigment and medium were precisely as he had left them. So were his Winsor amp; Newton Series 7 sable brushes, including the one with a telltale spot of azure near the tip that he always left at a precise thirty-degree angle relative to the others. It suggested the cleaning staff had once again resisted the temptation to enter his workspace. He doubted whether his colleagues had shown similar restraint. In fact, he had it on the highest authority that his tiny curtained enclave had displaced the espresso machine in the break room as the most popular gathering spot for museum staff.

He removed his leather jacket and switched on a pair of standing halogen lamps. The Deposition of Christ, widely regarded as Caravaggio’s finest painting, glowed under the intense white light.