I never thought it would happen to me. It happened to other mothers – yes, and fathers too. I’d seen them on the evening news, puffy-eyed, bewildered, blinking away tears. The camera zooms in to the photograph of the son as they like to remember him, in his school blazer (eyes still shining then) grinning toothlessly at the school photographer. Or the daughter as a teenager, astride a mountain bike in the Pyrenees, tanned and ponytailed.

I never thought it would happen to me. But in 2005 it did. I discovered my child Sacha, a man now, a man who had never practised yoga, slumped over in child-pose on a beer-stained rug; his alabaster back cold to my touch; a half-empty syringe at his side; daytime television drowned out by the weeping of his dogs and the howling of police sirens.

My future ambushed.

These mothers on the television – clutching handkerchiefs or their husbands’ hands – I used to think they put themselves through this ordeal in order to draw the public’s attention to a pressing social issue, start a campaign, establish a foundation to honour his or her memory. But then I understood they do it to avoid waking up in the morning with the feeling that the very heart of their lives has been surgically extracted without anaesthetic. Although they yearn to escape to the realm into which the beloved has made an untimely entry – without their permission – they’re too considerate to inflict this same agony on their living loved ones. So what do they do instead? They search for meaning; for a purpose to rein themselves back from the lurking abyss.

In the weeks that followed Sacha’s death I duly busied myself applying to a charitable trust for funding to set up a project to help teenagers who had been abused in childhood and who would, more than likely, go on to self-harm, harm others or abuse substances. But my burnt-out heart wasn’t really in it. I needed a break from that all-too-familiar world, and it was a relief when the funding didn’t come through.

The void continued to terrorise me. As a Buddhist I believed in the preciousness of life and the concept of ‘turning poison into medicine’: that suffering – however deep – could ultimately prove beneficial. But what value could possibly be created from this?

My daily mantra had become ‘Why me?… Why me?’

‘I’m not a junkie, Mum,’ Sacha used to say. ‘I’m someone with a habit.’

And I’d convinced myself I could help him break that habit. Defeat wasn’t an option I’d allowed myself to consider; too much was at stake.

My son wasn’t the archetypal junkie you see in the movies with hollowed-out, shifty eyes, greasy hair, and thieving, nicotine-stained fingers. Yes, he smoked roll-ups, but that was as far as it went. More than he loved heroin, Sacha loved ancient Hispanic history and climbing mountains.

For Christmas, the week before his death, he’d given me a large, glossy, illustrated book called Lost Treasures of the World. I read how the Conquistador Francisco Pizarro captured the Inca emperor Atahualpa in Peru and promised him his freedom if his people were able to fill a ‘ransom room’ full of gold. For months the Incas laboured day and night to bring gold and treasure from all over their empire. But once the ransom room was full, Pizarro killed Atahualpa anyway.

How I empathised with those Incas who, like me, had done everything, everything in their power, to save the person in danger. How cheated they must have felt after his death.

How cheated I felt.

It was, he said, the best Christmas he’d had for years. We had tears in our eyes as Sacha played the blues again on his harmonica. Finally on a decent drugs programme, I thought he’d turned a corner at last. Then, after some crazy partying on New Year’s Eve, one last fling resulted in what the coroner recorded as ‘accidental death from a heroin overdose’.

And I lost my treasure.

Peru stayed with me, though. Sacha’s ashes sat in a wooden urn – not on the mantelpiece but, out of respect for his shyness, tucked away in a corner of the living room under the voluminous palm tree he’d bought me many Mother’s Days ago. The ashes wanted to be scattered – but where? I already knew. I’d known all along.

For the last few years of his life, all Sacha had wanted was to go back to South America. Brought up in England but half Colombian, he’d travelled the continent extensively and had hiked the Inca Trail before it became a popular gap-year thing. He often recalled the moment when, dead on his feet with hunger and exhaustion, he reached the end of the trail and felt his spirit soar as he watched the sun rise over the Inca citadel of Machu Picchu.

‘One of the coolest moments of my life, Mum. When I’m better I want to see that sunrise again, and I want to take you with me.’

I had the feeling he still did.

But the perilous, futile trail of recovery we’d been limping along together for years had left me depleted and confused. I’d morphed into an auto-pilot-crisis-management zombie with no time to process where and why it had all gone wrong, or head-space to write about it. Some form of reflective, healing journey might be the answer.

But was Peru, with its Conquistadors, Shining Path Maoist guerrillas and heartbreaking poverty a sensible choice? It had never been on my tourist radar. The country was, however, home to that most sacred – and visited – site in Latin America, the site that Sacha most loved. So it would, quite simply, have to be.

Already, it was almost a year since he’d died, but was I brave enough yet to make the journey to Machu Picchu to scatter my son’s ashes? I’d spent the last few years fending off my terror of death; now I was afraid of life. The tectonic plates of my world had imploded. I was in fragments. There was a permanent knot in my stomach – the severed umbilical cord.

All I knew was that I had to go soon. And that I had to go alone.