Bill Hardy is on his deathbed when he fixes daughter Nell with a troubled, urgent stare. “You need to know that I’ve always loved you even though you were never really mine to love,” he tells her. His words are the catalyst for Hannah Beckerman’s third novel, a tangled tale in which the unravelling of family secrets exposes dilemmas of startling moral complexity.

Beckerman’s last book, If Only I Could Tell You, was similarly fraught with familial angst but offset estrangement and loss with flashbacks to a world of Rick Astley and Wagon Wheel biscuits. There is no such nostalgic relief here, though many a cup of tea is made and, as scientist Nell works to unpack the puzzle of her father’s parting utterance, alternate chapters carry the reader back in time to when a series of traumas transformed life for Nell’s mother, Annie, 35 years earlier.

There’s a sense of melancholy to these minutely observed pages that holds melodrama at bay, even as the psychological pain piles up. Though Annie is in the grip of dementia, Nell is not alone: as well as her father’s former business partner, Elsa, there’s a boyfriend who’s forever texting, and two older sisters. Even so, she finds herself in a bind that renders her unreachable. It doesn’t help that she’s not just considerably younger than those siblings and looks nothing like them, she’s also left their shared south London world far behind – first passing her 11-plus, then winning a place at Oxford.

While grappling with themes of identity and belonging, Beckerman liberally scatters red herrings to sustain the novel’s mystery. The ending provides resolution, but the book’s strength lies in its readiness to accept that life’s apparent dichotomies are sometimes no such thing. An act of kindness can feel like cruelty, truth can seem inseparable from lies. As for love, it’s impossible to have without grief, Beckerman declares. Grief is “love’s echo”.

• The Impossible Truths of Love by Hannah Beckerman is published by Lake Union (£8.99)