'I'm sorry,' the woman said eventually, her eyes not meeting Katie's.

Katie left the hotel gardens, her heart pounding. She moved along the beach, passing pairs of sunloungers placed at discreet intervals along the shore, where couples in swimwear lay reading or dozing. She averted her gaze from them and walked for some time, her sandals filling with warm, golden sand.

The sun was hot against the back of her neck and she thought vaguely that she should have applied suncream. When she was well beyond the resort, she sank down in the shade of a palm tree and hugged her knees. Her throat felt dry and she couldn't remember when she'd last drunk anything. She was weary with exhaustion and now wished she'd not left the cool of her room.

Katie rested her chin on her knees. Am I losing it, Mia? I don't seem to know myself any more. Does that surprise you? Me, of whom you once wrote: 'Katie knows who she is and strides confidently through the world.' Well, here's the thing: now I feel like I'm only tiptoeing.

I can't afford to stay here much longer, but I don't know what to do next. The thought of going back to England terrifies me. I honestly don't think I have the strength. Your journal was the only thing giving direction to my days, and without it I feel ... adrift. Hours seem to stretch out endlessly and, God, Mia, it's so lonely. I am desperately lonely.

Nights are the worst. I keep dreaming about you. You're on the cliff top and I'm beside you. We're arguing. You've just discovered that I've been reading your journal and you're furious with me. The wind is pushing your hair away from your face and I can see that your eyes are bright with anger. You demand the journal, but I don't answer you and we both listen to the waves crashing somewhere below. When you ask a second time, I tell you that I've lost it I carelessly left it in a hostel and went out for dinner, not giving it a second thought. You picture those beautiful cream pages and heart-worn words, lost, completely lost, and become so furious that you start shifting, not watching where you're putting your feet. You're pacing close to the cliff edge and I'm terrified that you're going to fall so I reach out, but instead of pulling you back to safety, I push you.

That's what I dream, Mia. Every night.

Her cheeks were wet with tears. They fell onto her knees and soaked into the loose hem of her dress.

'Katie?'

His voice was an electric jolt and her head snapped up.

He stood in front of her, a hand shading the sun from his eyes. His skin was pale and his hair had been cut short.

'Finn?'

He tried to conceal his shock at her appearance. Her grief was something physical; it was the dark shadows under her eyes and the thinness of her arms that hugged her knees against her chest. Her hair had grown darker and it seemed, for an absurd moment, as if he were looking at Mia.

'Finn?' She rose to her feet. 'Oh, God! It's really you!' She lurched forwards, throwing her arms around him.

He breathed in a scent caught in her hair and closed his eyes, folding himself into a memory.

Eventually, Katie pulled away, wiping her face and smoothing her hair behind her ears. She looked small and fragile, like a wilting flower starved of water.

She stared at him, shaking her head. 'What are you doing here?'

'Thought you could use a little company,' he said lightly. He wouldn't tell her that her voice had sounded so flat and lifeless when she phoned, it had scared him. He'd already let one Greene sister come here on her own; he would be damned if he'd make the same mistake twice.

'How did you know where I was staying?'

'I spoke to Jess.'

'She didn't say you were coming.'

'Apparently you're not so efficient at checking your emails these days,' he said with a smile. 'The two of us have been plotting. We didn't like the thought of you here alone.'

Her eyes turned glassy and it was a moment before she asked, 'When did you arrive?'

'Couple of hours ago. I got a taxi straight here. The guy on reception told me you'd be on the beach.'

She smiled at him for the first time. 'I can't believe you're here.'

'Shall we walk?'

They moved along the shoreline. A light breeze stirred the surface of the sea and small waves broke inshore. He could smell the sea in the humid air, but also something citrus that he couldn't place. 'Jess told me about your backpack,' he said eventually.

'Mia's journal was in it.'

'I know.' He glanced at her and saw she was biting her bottom lip.

'It feels like I've lost her again.'

'Hey,' Finn said, nudging her with his shoulder. 'What are a few pages of Mia's ramblings when you've got me here to recount all those travelling tales?'

Katie smiled.

'Anyway, it sounds like you're the intrepid traveller these days.'

'Not really.'

'Manage to do any camping?'

'No. I've stayed in a few hostels, though.'

'Katie Greene in a hostel? That's not something I would have believed.'

'I skydived, too.'

'No! In Australia? At the Slade Plains?'

'Yes.'

'And that from the girl who wouldn't jump a rock pool without doing a risk analysis first. I'm impressed.'

'Don't be. I hated it.'

He laughed.

'Mia loved it though, didn't she?'

'I swear I could see her grinning a thousand feet up!' He remembered her running over to him in her jumpsuit, her goggles pushed up on her head, her smile stretching into her eyes.

'You both had a lot of fun.'

'Yes,' he agreed.

'What did you do after Mia left for Bali?'

'I missed my flight to New Zealand, so I stayed in Aus. I hired a car and headed for the east coast.'

'Long drive.'

'Yes,' Finn said, thinking of the hot, dusty stretches of road, and the cool nights sleeping on the back seat of his car. 'I never made it.'

'Where were you,' she said seriously, 'when you found out about Mia?'

'At a gas station. It was in the middle of nowhere. They had an old computer hooked up to the Internet, so I logged on to check my mail. There were seven messages from my brother telling me to call home urgently. I lost my mobile a few weeks before, so no one had been able to get in touch with me. I paid the till girl $20 to let me use the office phone.' He remembered that she wouldn't allow him behind the desk, so he'd made the call leaning over the kiosk, a rack of mints pressing into his hip bone.

'My dad answered. I knew something had happened as he wouldn't speak to me, kept telling me to hold on while he found Mum. She was in the bloody bath. Took ages for her to get to the phone. I was sweating by the time she came on the line. She just said it outright: "Mia Greene has died. They found her body at the bottom of a cliff in Bali thirteen days ago." She had been dead for thirteen days and I didn't know,' he said, shaking his head.

'Afterwards, I hung up, got back in my car and drove off. I don't know what I was thinking. In fact, I wasn't thinking, it was like my mind went totally blank. Maybe the logic was that if I drove far enough away from that phone, then it wouldn't have happened.'

'Oh, Finn.'

He glanced out to sea where a speedboat raced across the water, the hull bouncing off the waves. 'I pulled in later at a beach and just sat on the shore watching the waves break until it was dark.' He'd cried and raged, and punched a tree so hard he dislocated a knuckle. 'Then I drove straight through the night to reach Adelaide Airport and took the first flight out of Australia.'

'Oh, Finn,' she said again.

'Anyway, that's enough of the happy talk for one afternoon,' he said, stopping and turning to face the sea. 'Eighteen hours on a plane I'm ready for a salt water bath.' He pulled off his T-shirt and tightened the cord on his board shorts. Then he ran into the clear water, wondering if every ocean would always remind him of Mia.

Katie watched him dive under the water. He surfaced, shaking his head, sending silver droplets flying through the air. Then he flipped onto his back and floated beneath the cloudless blue sky.

Finn is here. He is really here.

The sea glittered and the breeze seemed to skate off its surface, sliding over her skin. Two young girls with their hair in braids padded through the shallows, snorkel masks swinging from their hands. She smiled, thinking of Mia. Then she removed her sandals and stepped forward, sinking her bare feet into the wet sand at the edge of the sea. She concentrated on the feeling of salt water shifting beneath her toes, and then she took another step and let the sea spill around her ankles. It was warm and clear, inviting, not the cold sea of Cornwall.

She gathered the bottom of her dress with a hand and took another few steps until water reached her knees. She glanced up, checking Finn was still near. He waved and she managed to lift her hand and wave too.

He had asked her once, 'Why don't you swim in the sea?' They had been sharing a bath in his flat in North London, and the water had turned tepid, foam bubbles melting into a milky scum. She was leaning against his chest, her knees poking through the surface like two white hills, as she said, 'I almost drowned at Porthcray when I was 14. The tide turned while I was swimming.' She had run her fingers over the metal bath handle, wiping off flecks of water as she added, 'I'll never trust it again.'

He had leant forward and kissed her damp shoulder. It was the only response she'd needed.

Strange that she'd never told Ed about her fear of the sea, she thought now as she waded back out of the shallows, only Finn. She sat on the shore, pleased by the swirls of salt that dried on her shins. She turned her face to the sun and closed her eyes, feeling the tension in her neck loosening.

A few minutes later, Finn sank down beside her. The sun illuminated his face and she saw flecks of green in his irises. 'Finn,' she said slowly, sitting forward. 'Why are you really here?'

He picked up a stone and turned it through his fingers as he said, 'It's been hard back in Cornwall. I've felt sort of ... dislocated from everything. It was like I needed to be in Bali, to be there, where it happened, for it to seem real.'

She nodded. 'I felt the same.'

'Did you?'

'When the police told me, it was so surreal. I don't think I really believed it. Seeing her body helped, though. I needed to be certain.'

'That must've been hard.'

She nodded.

'When you rang a couple of weeks ago and said you were out here, I realized how much I needed to come to Bali too. What you're doing this trip, going to the places Mia did that makes total sense to me.'

'Does it? Sometimes I'm not sure it even makes sense to me.'

'You're searching for answers. I get that.'

'Am I? Or am I just running away?' She looked down at her hands.

'Katie?'

'Maybe this trip was never about Mia. Maybe I just used it as an excuse to escape my own life.' She thought of Ed, of her job, of her flat. She missed none of it. What did that say about the life she'd left behind?

'It's okay to be here for yourself too. It doesn't always have to be about Mia.'

For some time they sat on the shoreline listening to waves lapping against the sand. She could feel the skin on her chest prickling pink in the heat. 'I think I should find some shade,' she said eventually.

She gathered her sandals and as they started to walk, Finn said, 'So you went to Maui?'

'Yes. I visited Mick.'

He waited for her to continue, perhaps unsure how much Mia had committed to her journal.

'I know about Harley,' she said.

'Were you shocked?'

Katie nodded. 'I wish Mia had told me herself.'

'She wanted to.'

'But instead she told you.' She glanced away, surprised by the speed with which old jealousies could surface. 'Sorry. I didn't mean that. I'm grateful that you were there for her.'

A cloud passed over his face, something she couldn't understand. But just as quickly as it arrived, it vanished. 'I think Mia didn't tell you about Harley because she was afraid that being half-sisters would change things between you.'

'Maybe it would have. It was awful finding out. It felt ... I don't know ... as if it diluted us.'

Finn smiled. 'That's exactly what Mia said.'

'Is it?' Katie smiled too. 'But I don't feel like that any more. Half it's just a word, isn't it? We still grew up together, shared our childhood. Having different fathers makes no difference to me. We're sisters.'

'Exactly.'

'Sometimes it feels like I know more about Mia from her journal than from her. It's driving me mad that it's gone. I've had it in my hands this whole time but didn't read it all. I just keep thinking, what if she'd written something that would've explained things?'

'The police here must have examined it closely.'

'I've been told they would have. And I flicked through the last pages myself as soon as I found it.'

'And there was no note ... no clue as to what happened?'