Zen pressed the pause button of the remote control unit, stilling the video.

'Why are you up, mamma?' he asked, trying to keep his irritation out of his voice. This was breaking the rules.

Once she had retired to her room, his mother never reappeared. It was respect for these unwritten laws that made their life together just about tolerable from his point of view.

'I thought I heard something.'

Their eyes still held. The woman who had given Zen life might have been the child he had never had, awakened by a nightmare and seeking comfort. He got up and walked over to her.

'I'm sorry, mamma. I turned the sound right down…'

'I don't mean the TV.'

He interrogated those bleary, evasive eyes more closely.

'What, then?'

She shrugged pettishly.

'A sort of scraping.'

'Scraping? What do you mean?'

'Like old Umberto's boat.'

Zen was often brought up short by his mother's references to a past which for her was infinitely more real than the present would ever be. He had quite forgotten Umberto, the portly, dignified proprietor of a general grocery near the San Geremia bridge. He used the boat to transport fruit and vegetables from the Rialto market, as well as boxes, cases, bottles and jars to and from the cellars of his house, which the ten-year-old Zen had visualized as an Aladdin's cave crammed with exotic delights. When not in use, the boat was moored to a post in the little canal opposite the Zens' house. The post had a tin collar to protect the wood, and a few moments after each vaporetto passed down the Cannaregio the wash would reach Umberto's boat and set it rubbing its gunwale against the collar, producing a series of metallic rasps.

'It was probably me moving around in here that you heard,' Zen told her. 'Now go back to bed, before you catch cold.'