With a series of grisly murders as its backdrop, Joyce Maynard's latest book, After Her, tells the story of two sisters, Rachel and Patty, and their adored but flawed father, a homicide detective charged with finding the killer.

Loosely based on the true story of a serial killer who stalked the mountain trails in Marin County, Calif. in the late 1970s, it is also the tale of a dysfunctional family, but one with love at its core. It's a thriller, but it's also very much a love story.

After Her is narrated by 13-year-old Rachel. Her sister, Patty, 11, is her devoted and constant companion. They live with their depressed mother in a ramshackle house at the base of a mountain, which has been their playground for as long as they can remember.

After the first of a string of murders occurs, the girls are warned to stay off the mountain by their parents, especially their father, whose sudden celebrity status as he tries to catch the killer, imparts on Rachel a new-found popularity among her peers, who until now, have barely noticed her existence.

As she is swept away by her new friends into uncomfortable places and situations, her ever-faithful sister finds new occupations, which may be just as dangerous when framed by the imagination of a 13-year-old girl who believes she has the ability to "see things," including seeing into the mind of the killer.

To save her father, who is demoralized and suffering from the toxic effect his failure to apprehend the murderer has on him, and because she believes she knows what the murderer is thinking, Rachel hatches her own plan to lure the killer into a trap, so that her father can once more be the hero she believes him to be. Being a 13-year-old girl, she believes this is possible. When the killer turns the tables, it is her younger sister who saves her in a most unconventional way.

"I knew the girls would have to confront the killer," Maynard said in a recent phone interview. "I was really stumped for a long time. If an 11- and 13-year-old confront a killer, how are they going to survive? I didn't want the resolution to come from a big strong man with a gun. I wracked my brains and thought 'What would they do?'"

That resolution eventually came from a game the two women, whose story Maynard has adapted for this novel, used to play when they were children.

"These are girls who came of age in a pre-tech era. They didn't even have TV."

While the book is a work of fiction, its roots are real.

"The experiences of the book are true to the sisters," says Maynard. "This work gives me the chance to share other lives. I loved being with those women. They are just ordinary people. I love that."

Maynard, who often weaves her own experiences into her writing, got the opportunity here to share a childhood very different from her own.

"There is usually a lot of food in my work," says Maynard, "but in the story of these two sisters, left to their own devices, their mother doesn't cook for them. Their experience was so different from mine as a child. It's wonderful to imagine a different way to grow up," says Maynard.

"In a way, the fact the mother has checked out allows the girls to develop themselves," she adds. "It's very different than the powerful mother I had."

What also makes Maynard's story so real and so engaging is her ability to be 13-year-old Rachel and tell her story, along with all the magic and mayhem associated with that no-longer-a-child-but-not-yet-an-adult-either period in time. It's a time when life is made up of many layers, writes Maynard, and an adolescent has the uncanny ability to have a foot firmly planted in both worlds.

"Thirteen-year-old girls can actually believe that the reason they won't get to marry John Travolta is because he's got a girlfriend already," writes Maynard, "and that Peter Frampton's getting a haircut qualifies as a tragedy, and that receiving a call from a particular boy or a particular girl for that matter is the most wonderful thing that ever happened. Thirteen-year-old girls believe in heroic fathers and wicked stepmothers. They believe the words to songs, and the advice of other thirteen-year-old girls, and that the first boy they love, they will love forever."

To someone who once was a 13-year-old girl, Maynard's words ring true.

After Her is conceivably Maynard's best work of fiction to date. Her ability to reach back and share what it is like to be a prepubescent adolescent girl, makes for a story that is both poignant and exciting and very hard to put down.

After Her, which is published by Harper Collins, was released last month and is available at bookstores and online.