Her foot struck something and frantically she reached down into the water, diving, to find it: material, his jacket. She grabbed hold and kicked her legs hard to pull Robbie up to the surface. So heavy.

Thirteen years old, in the pool in Norwich with the other Girl Guides . . . She tried to remember her lifesaving lessons but the water there had been calm and tame. She kicked and kicked, got herself on her back with Robbie’s head leaning back against her shoulder, her arm around his chest, the other looped through the preserver. He was a dead weight in the water. His eyes were closed.

‘Robbie,’ she gasped, salt water in her mouth. She looked over her shoulder and the boat was several feet away. The rope anchoring the mainsail had come loose and the sail was flapping back and forth, useless for the moment, until it caught the wind by chance.

Emily kicked her legs, trying to get them closer to the boat. Robbie might be dead already: the blow might have been hard enough to kill him. He might have inhaled water and be drowning even now, even though she had his face out of the water. Dry drowning they called it. She couldn’t check for breathing or feel for a pulse: she was too busy swimming, and she didn’t dare. His mouth was open, his eyes closed, his skin pale. His hands floated just below the surface.

She kicked and kicked, holding him tight. Her shoes were stopping her so she toed them off, letting them fall away into the deep sea. Her skirt tangled around her legs. She wished she’d worn trousers. She thought about reaching the boat only not to be able to haul Robbie’s body aboard. What would she do? Cling on to the side, cling on to him, praying someone would come and rescue them? Had there been other boats out? She hadn’t noticed. But this was a busy place – surely someone would come by.

But when? Could she hold on to Robbie until then?

They could die here. They could both die. Not to embrace and to part, but to embrace and to sink, together, to wash up on the shore days or weeks from now. Their bodies returned to the families whom they had decided not to leave.

But they’d never know that. Christopher, and her parents, Polly, Robbie’s wife and son. They’d never know that Robbie and Emily had chosen them over their own happiness. They’d see this death as a betrayal: the two of them had died in illicit, snatched hours.

And if that didn’t happen? If she lived and he didn’t, if he was dead already and she had to live the rest of her life knowing she hadn’t saved him? Who, or what, would that be a betrayal of?

‘Please,’ she sobbed, kicking and kicking and getting nowhere, ‘please wake up, Robbie. Please. Don’t leave me alone.’

Water in her eyes, in her nose, in her mouth. Burning salt and his body wanting to drift away. Lightning flashed and thunder boomed, incredibly close. Her muscles ached and burned, her fingers clenched in the cloth of his jacket. His hair was a dark slick on his head. A wave hit them and her face went under.

She felt his arm tighten around her.

He was awake – he was alive.

The boat loomed blue and white out of the water. The hull was impossibly high. ‘Hold on,’ said Robbie, and she held tight to the rope while he hauled himself up on to the boat and turned to pull her up. Banging her ribs on the boat, knocking the breath out of her, scraping her legs, but then she was there. Safe. Gasping for air, shivering, holding tight to Robbie. He clung to her. His breath came in short gasps. It was raining now, hard, warm rain that made the air nearly as liquid as the ocean. The boat rocked.

‘I can’t do it,’ she said. Her teeth chattered. ‘I can’t do it.’

‘You can, you can do anything, you will be all right,’ he said, smoothing her wet hair back, kissing her wet cheeks with his wet lips. Thunder crashed. ‘You are OK. You are safe. I’m so sorry.’

She kissed him and tasted salt. She was shaking badly now. ‘I can’t leave you. I can’t – I thought you were dead.’

‘I’m not dead. I’m stupid. I’m all right.’ But she saw blood flowing down his face now, from where the boom had hit him. She touched it, wondering at its colour on her fingers, before instinct kicked back in and she pulled his head down so she could look for the wound. Her hands shook as she put pressure on it. She seemed to have no strength.

‘I thought you were dead and I’d lost you and it was the most terrifying thing I’ve ever felt,’ she told him through chattering teeth. ‘I thought about what it would be like going on living with you dead and I don’t want to do it.’

‘I’m not dead. I’m not dead. It’s all right.’ He soothed hands down her back.

‘I don’t want to live without you. I never want to live without you.’

He pulled back. There was blood on his face, and he was shaking now, too. Shock. Hypothermia, maybe, even in this warm water. They should get a blanket.

Lightning so close, it left an after-image on her retinas: Robbie’s silhouette in black and red. Thunder.

‘What are you saying?’ he asked.

‘I’m saying we’ve already betrayed them. We betrayed them from the minute we met each other. I can’t love him as I should, and you can’t love her as you should. If we’d died together, no one would know that we’d decided never to see each other again. We belong together. I can’t love anyone as much as I love you, Robbie. I can’t do it. I’ve tried and I can’t.’

‘What are you saying?’ he asked again, except this time he whispered it.

‘I can’t lose you again. It’s all hollow in the centre of things without you.’

He swallowed. Staring, pale, into her face.

‘I can’t lose you either,’ he said.

And he held her tight up against him, boat wandering free in the storm.

There were dry clothes in Robbie’s locker below. She rolled up the sleeves of his shirt and the hems of his trousers. He had only one rain slicker and she stayed below, shivering, wrapped in the only blanket, as he piloted the boat to shore. The cabin was tiny and steamed up immediately. She watched him through the hatch and thought about concussion and shock but her thoughts kept returning over and over to what they’d said. What they had done.

It was decided now, whatever would happen. She tried to summon something: joy, guilt, even fear. But she couldn’t seem to. That would come later. Right now she could only think: it was decided.

When they reached the marina, Robbie pulled the slicker over both of them to shelter them from the rain and they walked in step to a little hut with a palm canopy, with a rickety wooden picnic table underneath it.

‘¿Recibió mojado, Bob?’ called the woman in the window of the hut.

‘Sí. Cafecito, Analena.’

They sat at the picnic table and in a few minutes, the woman brought them two tiny cups of coffee. Emily drank hers down immediately: it was incredibly sweet and incredibly strong. ‘¿Podemos por favor tener otro?’ she asked the woman, who nodded. The rain drummed on the canopy and dripped from the palm fronds.

‘I can’t stop thinking of that piece of music,’ she said to Robbie. ‘The Bach we listened to, that night we met. It’s stuck in my head.’

‘The music that begins where it ends.’

‘And that ring. That ring you gave me, that I gave back to you.’

‘I still have it. It’s in a drawer at home.’

Her knee touched Robbie’s under the table.