Louise Penny on creating her beloved character, Inspector Gamache

Mystery author Louise Penny has sold more than four million books worldwide. Her 13th installment in the Chief Inspector Armando Gamache series, "Glass Houses," takes readers to the fictional Canadian village of Three Pines, where a mysterious figure appears on the village green – and trouble follows.

Penny joined "CBS This Morning" to discuss creating the detective at the center of the series and how her writing became her solace. 

The New York Times bestselling author says literary success came much to her surprise.

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"When I first started designing this series I didn't actually think – I wanted it to be published [but] I didn't actually believe it would be because it's hard. So I knew that the writing of it would probably have to be reward enough because it may be the only reward I would get," Penny said.

With that in mind, Penny set out to create a place in which she would like to live, filled with characters she would choose as friends.

Then, she set out to build the main character.

"Initially I thought, well, I'll make him a man at odds with himself, maybe some sort of an addict of some sort – an unhappy fellow. And then I thought, why?" she said. "If I'm lucky and I become connected to this character I don't want to get tired of him. So I thought, he has to be a man I would marry."

Penny's husband, Michael Whitehead, was the inspiration for Gamache. Whitehead passed away last year but remains Penny's inspiration.

"I never ever dreamed that I would find so much comfort in writing the books as Michael was dying. And I thought, honestly, that once Michael went I wouldn't be able to write anymore because he was my muse," Penny said. "Gamache is so infused with my husband that it has made him in many ways immortal."

Penny, a former journalist in Canada, began writing the books just after 9/11 and part of what she hoped to do was to create a "safe place" for those who, like herself, weren't feeling that safe.   

"I get letters from readers saying that reading the books is comforting for them, which means a lot to me," she said.

Penny's latest novel centers on the sudden appearance of a mysterious figure and the body found in its wake. Murder stories, for her, are a way to explore human nature.

"I think we're never more ourselves than when we are pushed. It's easy to be a decent human being when everything is going my way, but what happens when it's not? And that's when we see true character come out," Penny said.