Most people who talk of skeletons in family trees are speaking metaphorically. But there's an actual skeleton in the trunk of an old wych elm tree at the Hennessey family home in Dublin. Who is it? How long has it been there? And what does it have to do with Toby, the nice-guy narrator of Tana French's intricate and beguiling stand-alone mystery, "The Witch Elm"?

That the skeleton isn't discovered until a third of the way through the 500-page novel testifies to French's talent at immersing readers in mysteries that go beyond those of old bones. Having written six layered police procedurals featuring the Dublin Murder Squad, French now switches the perspective from police to crime victim.

Toby is a 28-year-old public relations exec who has always thought of himself as a lucky fellow until a brutal attack in his home fractures his skull and his sense of self. Doctors tell him he's lucky to be alive, but all Toby sees are the gaps in his memory, the slight slur in his speech, the difficulty in concentrating.

His family suggests he move in with his Uncle Hugo, a genealogist recently diagnosed with brain cancer, and so Toby and his supportive girlfriend Melissa arrive at Ivy House. Toby and his cousins Leon and Susanna spent idyllic times in the four-story home as kids and teens, running wild in the large, unkempt garden, and a sense of sanctuary remains. Then Susanna's young son finds a skull beneath the wych elm. Cue the detectives, doubt and suspicion.

Toby tries to sync his memories of his teenage years with those of mercurial Leon and practical Susanna, only to find his world shifting. While Leon was being bullied for being gay, and Susanna harassed for being a smart girl, Toby was everybody's pal, skating by on innate charm, mistaking privilege for luck. Memory, he realizes, is an unreliable narrator of events, even without a knock on the head. He is rightfully troubled by what he remembers — and what he doesn't. That the detectives consider him a murder suspect comes as a shock.

French often writes about the mutability of memory and questions of identity, as in her second novel, "The Likeness." Expected, too, are complex characters, spot-on dialogue, an atmospheric setting. But the pacing is slow and the tone reflective as Toby puzzles through the fragmented past. When he gets his best pals to recount the evening of his attack, it's as if he's hearing about someone else, "a favorite brother maybe, cocky and laughing and innocent enough to break your heart, at ease with all the world and his place in it, and now lost."

Tana French

Nancy Pate is a writer and reviewer who lives in Orlando, Fla., but wishes she was in Ireland.

The Witch Elm
By: Tana French.
Publisher: Viking, 509 pages, $28.