WHEN he sets out on a lonely moorland path he’s a grubby farm boy who knows little beyond the walls of Wuthering Heights. Three years later he returns a wealthy, educated gentleman - whose charismatic charm belies a psychopath hell-bent on revenge.

Where does Heathcliff go when he leaves Wuthering Heights? What turns him into someone capable of casual cruelty, rape and murder?

Ill Will, by Bradford writer Michael Stewart, is the untold story of Heathcliff from Emily Bronte’s passionate novel. Beaten and humiliated by Hindley, his tormentor, and betrayed by Cathy, Heathcliff sets out to discover where he came from, and gain the means to ruin the Earnshaws. What unfolds is a dramatic 18th century road trip, from Haworth moors to Liverpool’s docks, teeming with all walks of life. Compelling and beautifully written, Ill Will is a haunting re-imagining of Emily Bronte’s mystery, and a timely tribute in her bicentenary year.

Now one of the world’s leading production companies, Kudos, plans to turn it into a TV drama.

When considering Heathcliff’’s missing years, Michael - novelist, lecturer and Head of Creative Writing at the University of Huddersfield, whose work includes novels King Crow and Cafe Assassin and short fiction collection Mr Jolly - focused on Mr Earnshaw’s journey to Liverpool, and his return with a dark-skinned foundling. In Ill Will, the links between Liverpool’s early industrial glory and the slave trade are interwound with Heathcliff’s story.

“Why did Earnshaw walk to Liverpool, when he had horses and could’ve gone by coach? He went to get something and he came straight back. He was on a mission,” says Michael. Without revealing too much, this Earnshaw isn’t the kindly father of Bronte’s novel. You wonder whether, in bringing Heathcliff home, he was seeking redemption; a theme explored in Ill Will through despicable industrialist turned pious “do-gooder” Jonas Bold.

“Liverpool was Europe’s biggest slave port. Slave women were routinely raped, and both male and female slaves were subjected to unimaginable acts of depravity,” says Michael, who read meticulously recorded incidents of abuse in plantation diaries at Liverpool’s International Slavery Museum.

In Ill Will, Heathcliff is sickened by Bold’s accounts of “each and every sexual congress during his years on the plantation”. Learning of the brutal treatment of his mother sparks Heathcliff’s fury, simmering through years of Hindley’s abuse. “He’s been beaten, spat on, kept in a shed. All that anger and resentment has to come out,” says Michael. “I once worked in Wakefield Prison, with lifers who seemed like quiet, polite men, and when I heard their stories there was a catalyst which released something in them.”

It was reading John Sutherland’s book Was Heathcliff a Murderer? that gave Michael his idea. “I wrote the first chapter in 1995. I knew nothing about the 18th century North. I had a lot of research to do, but I was a mature student, immersed in studies, so it went on the backburner,” he says.

Years later, a sabbatical from Huddersfield University gave him time - not just to devour history books, but to re-trace Earnshaw’s journey, walking 65 miles from Top Withens to Liverpool in three days. “I did 20 miles a day, with a one-man tent and a dog. I was nowhere near Earnshaw’s brisk pace - he was there and back in three days, carrying a child, a fiddle and a whip!” smiles Michael.

Ill Will creates a fascinating sense of the 1780s North on the cusp of industrialisation. Manchester and Liverpool were under construction, along with the “Duke’s canal” linking the cities. It was a time of press gangs and unrest. Through Michael’s intricate detail we learn of people at work and leisure, the food they ate, language they used and clothes they wore.

“It was a turning point,” he says. “Through Heathcliff, we see it from the ground - poverty, misery, gin houses, children half-starved and deformed by child labour. Heathcliff leaves agricultural work for the city. Initially he reaches Manchester, and the beauty and cruelty of the Industrial Revolution. The Enclosure Acts were kicking people off their land, rural communities were lured into cities by the promise of better wages and ended up working 14-hour shifts in factories. Farm work was tough but it was in daylight hours - in the cities these vast cathedrals of industry ate up labour.”

Arriving in Manchester, Heathcliff is greeted by "much commotion and mulling about".

"I was taken first by the sights, then the sounds, and finally the smells. The town in front of us was like nothing I had ever seen...Ladies and gentlemen of fine attire. Some wore fancy clothes, silk coats and embroidered waistcoats. Brightly coloured frocks, ribbons and outlandish nosegays. But also there were those in tattered rags, ravelled dugs and barefoot.

"The buildings towering above us, reaching up to the clouds, were fit for giants...Spires that pierced the blue canvas of the sky. My ears were pricked with the clamour of industry. The clanking of metal plates. The clatter of iron-rimmed cartwheels on cobbles. Shouting, laughing wailing...The stench of burning coals, of rotting offal and festering fruits. A beggar sleeping in the gutter. A painted chaise pulled by fine mares. I saw the drive crack his whip and drive over the fingers of the beggar, slicing through two of them as though they were breakfast sausages.

"This was a place where you had to keep your wits about you. The vision before me was one part heaven and one part hell. I could barely decide what to make of it."

Michael was struck by how many social issues of the time are still around today. "With cities came homelessness. Walk through any city today and you’ll see people sleeping on streets. Immigration was a talking point in the 1780s, with resentment about Irish immigrants coming over for work. And slavery, one of the worst crimes in history, is back on the agenda. There are more slaves in the world now than in the 18th century,” he says.

Emily Bronte would have been aware of such social issues. “Patrick Bronte was an abolitionist, he was mentored at Cambridge by William Wilberforce. He championed workers’ rights and women’s rights. He addressed his children as adults, particularly after the death of Maria, their mother, and he made them socially aware. We see that in their writing,” says Michael, who lives in Thornton, where the Bronte siblings were born. “It wasn’t legal to have slaves here but people got round it by calling them servants, there was a well known case of a slave escaping from Colne who went on the run. A massive thing in Yorkshire, I’m sure Emily would’ve heard about it.”

When Andrea Arnold’s 2011 film of Wuthering Heights featured a young black Heathcliff, it caused a stir. Have purists reacted to Michael’s take on the anti-hero? “From Laurence Olivier to Tom Hardy, white men have played Heathcliff. But there are references to his dark skin in Wuthering Heights,” says Michael. “The idea that he was black doesn’t stretch the imagination too much, you wouldn’t think it’d be a big deal. Yet when I did an event at the Bronte Parsonage recently and the Bronte Society put it out on audio file, someone in America was outraged by a black Heathcliff!”

Heathcliff's obsession with Cathy is never far away in Ill Will, which he narrates as if he's talking to her. And we learn more about what makes him tick. For Michael, the fascination with Heathcliff lies in his paradoxical personality. “Characters in Victorian novels are either good or bad. In Oliver Twist, we know that Bill Sikes is a baddie and Nancy is a goodie. Heathcliff is two extremes in one person, his psychology is much more complex and knotty,” says Michael. "Emily Bronte spends the first part of her novel creating all this empathy for him, then throws it back in your face."

In Ill Will, Heathcliff reveals a flicker of compassion towards Emily, a worldly-wise highwayman’s daughter. The pair roam moors and towpaths like outlaws in a Western and, using Emily’s apparent ability as a medium, carry out graveside scams. “Emily knows the highwayman’s life, which was coming to an end in 1780, with turnpikes and canals being built,” says Michael.

Was he tempted to explore the rest of Heathcliff’s missing story? “Once he’s made his money he gets an education, there’s not much more to say,” says Michael. "I thought about him being press-ganged and taken to America to fight in the War of Independence, or trying to trace his mother back to Africa. In the I decided to leave it as it was. It was those first three months I felt were crucial.”

* Ill Will, published by HQ, HarperCollins, £12.99.