In 1899, psychoanalyst Sigmund Freud published a book entitled The Interpretation of Dreams, in which he laid out his theory of how dream interpretation can allow one to explore the unconscious. His belief – which slowly became a talking point among academics and doctors of the mind – was that we dream because our subconscious is trying to solve a problem or resolve a conflict, and that often dreams are not what they appear to be, but must be interpreted. He wrote: ‘The interpretation of dreams is the royal road to a knowledge of the unconscious activities of the mind.’

But why is it important to interpret dreams? Surely they are mainly nonsense? Sometimes, perhaps. But when a dreams are haunting, perhaps even repetitive, there is a clear sense that the subconscious is attempting to communicate a point; to create a realisation that can lead to meaningful change and a more peaceful inner world.

I revisited the works of Freud when writing my latest novel, Legacy. My heroine, Luna, prides herself on being a woman who is in control: organised, intelligent, capable. A successful scientific journalist, she has no need of unruly emotions – and yet, somehow, they are plaguing her.

At the very start of the book, I introduce you to Luna at work, and you see how cool, calm and collected she is. But I also give you a glimmer of her private world, as revealed through her disturbed sleep:

The dream had come again last night. She had woken suddenly, as she always did, clammy and panting, her deafening heartbeat thumping against her ribs, her own pleading voice echoing loudly in her ears.

This nightmare haunts Luna, following her all the way to Andalucía, Spain, where she has been commissioned to write an exposé on a medical clinic. This is the scene into which her subconscious plunges her time and again:

He was in the room, she could tell. It was dark, with shadows falling across her bed from the open window. A hot night. Too hot.

The sound of her door was a slow creak, closing shut with a click. She couldn’t move. Why couldn’t she move? It was as though she were paralyzed from the neck down.

She tried to speak but no sound came out.

Panic gripped her throat as she tried to shout. She could hear him moving around the room, getting closer. Was she in Cádiz or at home in California? All she knew was that he was coming for her.

Her head thrashed from side to side as the footsteps moved softly towards her.

‘Sshhhh, Luna.’

No. No. No.

Luna does not understand how to interpret the dream, but she has the strong sense that the meaning is deeply rooted in her psyche. Interpretation seems difficult – and very frightening.

In the meantime, Luna’s recurrent nightmare is joined by a new kind of dream, this one just as unsettling but entirely more pleasurable: Luna begins to dream, day and night, of being with her boss, Ruy.

Ruy had been with her all night in her dreams. Obscurely aware of a tangle of limbs and the racing of her blood, she surfaced from sleep, needy and aching, tormented by the lingering sense of his mouth on her body. The fading memory of the dream left behind it half-echoes of whispered words and wild, untamed emotions.

These new dreams require no interpretation. Still, acting on their meaning is not a simple matter. Luna has a tendency to shy away from dreams, from longings and fantasies: ‘with dreams there must come a time of awakening,’ she thinks. She believes this awakening is a way to protect herself.

But is Luna right to shun dreams in favour of reality? Is the distinction between the two even absolute?

As Alfred Lord Tennyson put it: ‘Dreams are true while they last, and do we not live in dreams?’ We should, according to one my favourite writers, Victor Hugo, strive to merge dream and reality. He wrote: ‘Each man should frame life so that at some future hour fact and his dreaming meet.’

For Luna, that means bringing her nightmare into the daylight; letting it be real; confronting what it means and why it is haunting her. If she can find the courage and the faith to do this, then perhaps she can also bring her dreams of Ruy into the light; perhaps those sensual moments she spends in his arms on a fantasy plain can become real. Perhaps she can, as goes the modern saying, ‘live the dream’ conjured by her own desire.