Author Irvine Welsh. (Shannon Stapleton/Reuters)

While other gritty novelists tend to flounder among sleazy topics and ineffective controversy, Scottish author Irvine Welsh keeps discovering new themes waiting among the murkiest aspects of human nature.

Crime, Welsh's latest book, features the re-emergence of one of his cruelest characters: Det. Insp. Ray Lennox, a brutal, tortured bigot from his cop story Filth (1998). In that previous book, Lennox's life was ruled by illicit sex, cocaine and the desire to fit in with his department's crumbling old boy's network. In Crime, the Edinburgh cop ("polis" in Scotch dialect) arrives in picture-perfect Miami on holiday with his girlfriend, Trudi. Lennox has become semi-respectable in the intervening years. Trudi is a well-balanced and successful woman, and Lennox is helping her plan their wedding. Nonetheless, his mental health is fried — he's severely traumatized by a girl's murder he failed to prevent. The dissonance raging inside Lennox compels him to explore the unknown city alone. He ends up following two wayward women in a shabby bar one night and discovers a ring of Florida pedophiles.

"Crime had to be different because child molestation is so boring to write about," says Welsh over the phone, speaking about the change in his subject matter. "With heroin users, their stories are sometimes genuinely sympathetic, because there are problems in society that drive people to drugs. But that isn't why pedos go after children."

Lennox ends up separated from his fiancé, battling to save an unprotected 10-year-old girl named Tianna from a group of sexual predators. Lennox is a bad man trying to scrub the grime off his coffin-nail soul, while Tianna is a prematurely sexualized child who becomes infatuated with her defender.

"I got my inspiration from living in Ireland," says Welsh, who currently resides in Dublin with his American wife. "There are constantly stories about clergy abusing children being reported on television and in the newspapers there."

If his oeuvre teaches us anything, it's that Welsh likes to explore the effects of disaffection, corruption and addiction. Trainspotting (1993) — which has sold over a million copies worldwide — features a group of chatty, philosophical drug abusers who are gradually undone by heroin. Marabou Stork Nightmares (1995) is about an unhappy systems analyst who falls in with a soccer hooligan gang that's into kidnapping and rape. The Bedroom Secrets of the Master Chefs (2006) is told from the perspective of a young party animal who develops an irrational hatred for a nerdy coworker; the latter's seemingly uneventful life of model trains and science fiction memorabilia becomes a foil for the protagonist's own boozy demons, and his inevitable downward spiral.

(Jonathan Cape)

In Crime, Welsh's distinctive narrative brogue crackles as brightly as it did in his first book, but here, he reveals something more powerful than depravity — the possibility of redemption. The soft-spoken, 50-year-old writer attributes this achievement to the necessities of the material.

"There's no moral ambiguity in pedophilia," Welsh says. "And there's no black humour in it, either. Pedophiles aren't interesting at all; they're just evil. That's why I wrote the book as a sort of existential thriller — the pages need to fly by for the readers so they're not dwelling on the issues. The subject matter itself isn't that compelling."

Welsh says he is inspired by the survivors of abuse, paraphrasing that oft-quoted maxim by Nietzsche: "Whatever doesn't kill you makes you stronger, I guess." Crime doesn't exploit the shock value embedded in the story; Welsh sees that as a dead end. But that doesn't mean he's playing nice. If anything, Welsh thumps hard on commentators who he feels lack clarity on the issue of pedophilia.

"The literary community's response to Lolita still makes me uneasy," he says. "The sex offender in it was an upper-middle-class aesthete, and sometimes people seem to think that's almost a way of justifying his crimes. Not that I want to attack Nabokov or his book, but society today doesn't look at child abuse the same way it used to, and Crime regards abusers in a completely different way."

In Lolita (1955), Nabokov portrays the pedophile Humbert Humbert as a libertine, suave and educated, transcending mainstream morality. Humbert's mind is a fascinating labyrinth: he justifies his abduction of Lolita as a sort of esthetic act, a love of beauty that is as misleading as it is sinister. By comparison, in Crime, the pedophiles are just sordid; they're weak beasts searching for another easy feed. The fury that Lennox feels for them is likely to be shared by the reader. Crime recognizes the extraordinary demands society places on police.

"Being a cop is an almost impossible job to do," says Welsh. "If you're at a desk working out traffic reports all day, that's fine. But if you're dealing with serial killers and sex offenders, that's right on the edge of experience. It compromises the human perspective. Where do you go after you see these things?"

Even so, Welsh still regards Crime as a fundamentally uplifting story.

"It's a more positive book for me," he says. "Usually I write about people making mistakes and how those mistakes get compounded. Crime's not about people falling apart. It's about characters coming together."

John Keillor is a writer based in Toronto.