‘You can’t come with me,’ said James angrily. ‘I can’t be responsible for you, and I need you here, to help us get away.’

‘Vengo con voi,’ she repeated and James pushed her roughly backwards.

‘Stay,’ he said as if to a dog and wished that he could speak her language properly. He put the goggles back on, grabbed the fins and moved towards the canal, but he sensed movement behind him and turned to see that she was following him.

‘Please,’ he said, desperately. ‘You can’t come. This is my problem, not yours.’ He pushed her back again, more gently this time, and turned away from her, but she suddenly leapt at him, knocking him over. Restricted by the goggles, he couldn’t see what was happening clearly and fell awkwardly, hitting his head on the hard ground. He twisted on to his back and tried to wrestle her off, but he was winded and she was lithe and muscular. It was like trying to fight with a wild animal. He didn’t want to hurt her, and had to put his hands up to defend his face as she landed a rain of vicious slaps down on his head.

Then there was a flash of steel as she whipped out her knife and held it to his throat.

They waited like that for some time before James realised that she was crying. A salty tear fell and landed on his lips. He took off the goggles and put up his hand to dry her cheeks.

‘Amy,’ she said quietly, then rolled off him and turned away in a sulk.

‘Yes, Amy,’ said James, harshly. ‘Is that was this is about? Look. I’m going to get her, all right? Not because she’s my girlfriend, or any nonsense like that, but because I promised I would. I don’t love her. I don’t love you. But I need you, and I need you alive. So stay here.’ He stood up. ‘Look, I know you can’t understand what I’m saying,’ he said more gently. ‘But I’ll be grateful to you for as long as I live. It’s just that, if you come with me it’ll make my job twice as hard.’

He picked up the fins and touched her on the back. ‘I will come back,’ he said. ‘Wait for me.’

He took four steps, then ran back and kissed her hard on the mouth. He left her there, frozen in surprise, her jaw hanging open and her eyes wide, and ran down to the aqueduct before she knew what to do.

He ripped off his shoes and slung them in his knapsack, which he strapped over his belly so that it wouldn’t stick up, then he put on the fins and goggles and lowered himself into the canal.