Zen recognized Anna Romizi from the photograph of her as a young mother which Carlo had kept on his desk, their twin baby boys on her lap. Now those fresh, plumpish features had been rendered down to reveal the bedrock Mediterranean female beneath, grim, dauntless, enduring. Zen said his piece and left as soon as he could, fearful and depressed at this reminder of the primitive, messy plumbing on which all their lives ultimately depended. It didn’t seem remotely surprising that it should break down without warning. On the contrary, the miracle was that it ever functioned in the first place. In growing panic he listened to the thudding of his heart, felt the blood coursing about the system, imagined the organs going about their mysterious, secretive business. It was like being trapped aboard an airplane piloted by an onboard computer. All you could do was sit there until the fuel ran out, or one of the incomprehensibly complex and delicate systems on which your life depended suddenly failed.

Which is what he thought had happened when the darkness abruptly enveloped him. He was on foot at the time, heading for an address in the heart of the old city. The same raw November evening which had culled the congregation in St Peter’s kept people indoors. The streets were lined with small Fiats parked nose to tail like giant cockroaches, but there was no one about except a few youths on scooters. Zen made his way through the maze of the historic centre by following a succession of personalized landmarks, a painted window here, a patch of damaged plasterwork there, that rusty iron rib to stop men peeing in the corner. He had just caught sight of the great bulk of the Chiesa Nuova when it, and everything else, abruptly disappeared.

In different circumstances the wails, groans and curses that erupted from the darkness on every side might have been distinctly unnerving, but in the present case they were a welcome token that whatever had happened, Zen was not the only one affected.