Is it circumstance or character that makes a person commit murder? "To be honest, I'm still not sure what the answer is," says Mary Swan, who grapples with that question in her Giller-nominated book, "The Boys in the Trees."

In the prologue to Swan's first novel, a young boy named William Heath climbs a tree to escape a beating by his vicious father. Hidden in the safety of its branches, the child carves his name into the craggy wood and vows that one day people will know his name.

Heath's wish is granted in Swan's gripping book. Sadly, it destroys his life.

Set in the late 19th-century, Heath commits a ghastly crime in Swan's fictional town of Emden, Ontario. The events are based on a grisly historical tidbit Swan discovered while working in the reference department at the University of Guelph library.

"I found this news item about a man who killed his wife and daughters in the late 1880s. He headed to Toronto to murder his son but was arrested, brought back to Guelph and executed," Swan told CTV.ca.

That item, plus current news stories about family slayings across the United States, started churning in Swan's mind.

Local history inspires Swan's tale of crime

"The thought of any public execution taking place in this country seems so unbelievable to us today. But it happened. It's a part of Canadian history," says Swan, who threw herself into studying Canada's execution process from days gone by.

Heath, the book's lynchpin, is a struggling bookkeeper in England who has lost yet another job. He persuades his wife to move to Canada after they lose their children to diphtheria.

Parents again by 1888, the couple and their two daughters continue to struggle in Emden. Then one day the unthinkable happens. The Sunday school teacher loses his job, purchases a gun and calmly shoots his family dead.

Swan's characters try to fathom Heath's motivation for his heinous crime. Was Heath crazy? Was he trying to protect his family from further pain? The process forces everyone to dust the cobwebs from their own shameful deeds and weigh right from wrong.

"A crime has a way of reverberating across an entire community. I wanted to see how an act like this would impact all kinds of people in a small town," says Swan.

"Today we hear of grief counsellors going into schools when tragedies like this happen. But what can you really say to people? The act is made so much more horrific because it's committed by a parent -- someone you're supposed to trust."

Eventually the boys of Emden climb the trees outside William's jail cell, vying for the best spot to watch him hang for his grisly deed. Before that happens, however, Swan makes readers think long and hard about coping with life's injustices.

"Some readers may blame circumstance for William doing such an unspeakable thing. Others may put the blame on William's character flaws," says Swan. "Humans are so complex. There's no one easy answer behind the things they do, particularly murder."

A good day to do laundry

Learning of her Giller nomination while she was doing the laundry, Swan says, "I'm still taking the news in. To say that I was shocked is no lie."

Known for her painstakingly crafted characters, Swan's previously published short story, "The Deep," won the prestigious O. Henry Award in 2001. Random House in the United States issued that work in 2003 in a single volume called, "The Deep and Other Stories."

Glad that readers all over the world are embracing her latest novel, as well as those of other Canadian authors, Swan says, "When I worked in a public library in the late 70s Canadian books had red flags on their spines. They were rare if you spotted them on the fiction shelves."

As Swan says, "There has been such an incredible change in Canadian literature over the last 30 years. We've got all kinds of different genres coming out of this country. That 'Group of Seven' mentality that once defined all the arts coming out of this country is long gone."