They looked so young, these students, these freshers – like babies. Did she and Sebastian ever look that young? It seemed impossible, somehow. It was harder still to imagine anything bad ever happening to those innocent, unblemished faces. And yet she wondered how many of them had tragedy waiting in their future.

Mariana’s mind went back to that poor girl, murdered by the marsh – whoever she was. Even if she wasn’t Zoe’s friend Tara, she was someone’s friend, someone’s daughter. That was the horror of it. We all secretly hope that tragedy will only ever happen to other people. But Mariana knew, sooner or later, it happens to you.

Death was no stranger to Mariana; it had been her travelling companion since she was a child – keeping close behind her, hovering just over her shoulder. She sometimes felt she had been cursed, as if by some malevolent goddess in a Greek myth, to lose everyone she ever loved. It was cancer that killed her mother when Mariana was just a baby. And then, years later, a horrific car crash claimed Mariana’s sister and her husband, making Zoe an orphan. And a heart attack crept upon Mariana’s father in the olive grove, leaving him dead on a bed of sticky, squashed olives.

Finally – and most catastrophically – there was Sebastian.

They had so few years together, really. After graduating, they moved to London, and Mariana began the circuitous journey that ended in her becoming a group therapist, while Sebastian worked in the City. But he had a stubborn entrepreneurial spirit and wanted to go into business for himself. So Mariana suggested he speak to her father about it.

She should have known better, really – but she cherished a secret, sentimental hope that her father might take Sebastian under his wing, bring him into the family business; let him inherit, before passing it on, one day, to their children. This was how far Mariana’s imagination carried her – but she knew better than to mention any of this to her father, or Sebastian. In any case, their first meeting was a disaster – Sebastian flew to Athens on a romantic mission, to ask permission to marry Mariana – and her father took an instant dislike to him. Far from offering him employment, he accused Sebastian of being a gold-digger. He told Mariana he would disinherit her the day she married Sebastian.

The irony was that, in the end, Sebastian did go into shipping – but at the opposite end of the market to her father. Sebastian turned his back on the commercial sector, instead setting up businesses to help transport much-needed goods – food and other essentials – to vulnerable and underprivileged communities around the world. He was in many ways, Mariana thought, the mirror image of her father. And this was a constant source of pride for her.

When the troubled old man eventually died, he surprised them all once again. In the end, he left Mariana everything. A fortune. Sebastian was astounded that, being as wealthy as he was, her father lived the way he did – ‘I mean, like a pauper. He got no enjoyment out of it at all. What was the point of it?’

Mariana had to think for a moment. ‘Security,’ she said. ‘He believed all the money would protect him, somehow. I think – he was afraid.’

‘Afraid … of what?’

For this, Mariana had no answer. She shook her head, at a loss. ‘I’m not sure he knew himself.’

Despite this inheritance, she and Sebastian indulged themselves with only one extravagant purchase: they bought the little yellow house at the foot of Primrose Hill, which they had fallen in love with at first sight. The rest of the money was put aside – at Sebastian’s insistence – for the future, and for their children.

This issue of children was the only sore point between them, a bruise Sebastian couldn’t help pressing on every now and then, bringing it up after one drink too many, or during a rare broody moment. He desperately wanted children – a boy and a girl – to complete the picture of the family he had in his head. And while Mariana also wanted kids, she wanted to wait. She wanted to finish her training and establish her psychotherapy practice – which might take a few years, but so what? They had all the time in the world, didn’t they?

Except they didn’t – and this was Mariana’s only regret: that she had been so arrogant, so foolish, as to take the future for granted.

When, in her early thirties, she consented to start trying, she found it difficult to conceive. This sudden and unexpected stumbling block made her anxious – which her doctor said wouldn’t help.

Dr Beck was an older man with a fatherly air, which Mariana found reassuring. He suggested that, before embarking on fertility testing and possible treatment, Mariana and Sebastian go away for a holiday, away from any kind of stress.

‘Enjoy yourselves, relax on a beach for a couple of weeks,’ Dr Beck said with a wink. ‘See what happens. A little relaxation can often work wonders.’

Sebastian wasn’t keen – he had a lot of work lined up and didn’t want to leave London. Mariana later discovered he was under a great deal of pressure financially, that summer, as several of his businesses were struggling. He was too proud to come to her for money – he’d never once taken a penny from her. And it broke her heart to find out, after his death, that he had been carrying around all this unnecessary worry about money for the last few months of his life. How could she not have noticed? The truth was, she was selfishly consumed with her own worries, that summer, about having a child.

And so she bullied Sebastian into taking two weeks off, in August, for a trip to Greece; to visit Mariana’s family’s summer home – a cliff-top house on the island of Naxos.

They took a plane to Athens, and then, from the port, they got the ferry to the island. It was an auspicious crossing, Mariana thought – not a cloud in the sky, and the water was calm and glassy flat.

At Naxos harbour, they hired a car, and drove along the coast to the house. It had belonged to Mariana’s father and now, technically, to Mariana and Sebastian – although they had never used it.

The house itself was dusty and dilapidated – but stunningly situated, perched on a cliff overlooking the deep blue Aegean Sea. Steps had been carved into the rock, going down the cliff face, leading to the beach below. And there, on the shore, over millions of years, infinite pieces of pink coral had broken up and mingled with grains of sand – making the beach glow pink against the blue sea and sky.

It was idyllic, Mariana thought – and magical. She could feel herself relaxing already, and felt secretly hopeful that Naxos might perform the little miracle that was being asked of it.

They spent the first couple of days unwinding and lazing on the beach. Sebastian said that in the end, he was glad they had come – he was relaxing for the first time in months. He had a schoolboy habit of reading old thrillers on the beach, and he lay in the surf, happily engrossed in The ABC Murders by Agatha Christie, while Mariana slept under an umbrella on the sand.

Then, on the third day, Mariana suggested driving up into the hills – to see the temple.

Mariana remembered visiting the ancient temple as a child, wandering the ruin and investing it with all kinds of magic in her imagination. She wanted Sebastian to experience it. So they packed a picnic, and set off.

They took the old, winding mountain road, which got narrower and narrower as they climbed higher into the hills, eventually deteriorating into a dirt track littered with goat droppings.

And there, at the very top, on a plateau – was the ruined temple itself.

The Ancient Greek temple was built from Naxian marble, once gleaming but now dirty white and weather-beaten. All that stood, after three thousand years, was a handful of broken columns silhouetted against a blue sky.

The temple was dedicated to Demeter, goddess of the harvest – goddess of life – and to her daughter, Persephone – goddess of death. The two goddesses were often worshipped together, two sides of the same coin – mother and daughter, life and death. In Greek, Persephone was known simply as Kore, meaning ‘maiden’.

It was a beautiful spot for a picnic. They laid out the blue blanket under the dappled shade of an olive tree, and unpacked the contents of their cold-box – a bottle of sauvignon blanc, a watermelon, and chunks of salty Greek cheese. They had forgotten to bring a knife – so Sebastian smashed the watermelon against a rock like a skull, breaking it into bits. They ate the sweet flesh, spitting out the bony seeds.

Sebastian gave her a messy, sticky kiss. ‘I love you,’ he whispered. ‘Forever and ever—’

‘—and ever and ever,’ she said, kissing him back.

After the picnic, they wandered the ruins. Mariana watched Sebastian clambering up ahead, like an excited kid. And as she watched him, Mariana said a silent prayer to Demeter, and to the Maiden. She prayed for Sebastian and for herself – for their happiness – and for their love.

And as she whispered this prayer, a cloud suddenly snaked in front of the sun – and for an instant, Sebastian’s body was thrown into darkness, silhouetted against the blue sky. Mariana shivered, and she felt afraid without knowing why.