The boat banged and buffeted its way through the short, hard waves, swathes of spray drenching the decking and the windows of the helmsman’s cabin. Zen’s cigarette obliged him to stand outside, at the top of the stairs leading down to the saloon. It was rush hour, and the boat was packed with school-children and commuters. They sat or stood impassively, reading papers, talking together or staring blankly out of the windows. Apart from the pitching and rolling, the crunch of the waves and the draughts of air laden with salt, not fumes, it might almost have been the bus which Zen took to work every morning in Rome. He eyed the children hunched under their satchels, chattering brightly or horsing about. They thought this was normal, he reflected, as he once had. They thought everywhere was like this. They thought that nothing would ever change.

At Fondamente Nove, Zen changed to avoid the detour to Murano. It would have been quicker to get off at the next stop, by the hospital, and walk through the back streets to the Questura, but as he was in plenty of time he rode the circolare destra through the Arsenale shipyards and out into the sweeping vistas of the deep-water channel beyond. The wind’s work was even clearer here, cutting up the water into staccato wavelets breaking white at the crest. They slapped and banged the hull, sending up a salty spindrift which acted as a screen for brief miniature rainbows and coated Zen’s face like sweat.

When they reached the Riva degli Schiavoni he disembarked, crossed the broad promenade, bustling even at that hour, and plunged into the warren of dark, deserted alleys beyond. He was largely following his nose at this point, but it proved a good guide, bringing him out on a bridge leading over the San Lorenzo canal near the three-storey building which housed the police headquarters for the Provincia di Venezia.