Four years ago, two of Mina Smallman’s grown-up daughters failed to come home from a summer evening picnic in the park.

Vanishing like this was out of character for Bibaa, who had been celebrating her 46th birthday, and 27-year-old Nikki. So when the police didn’t launch an immediate search of the park, her friends and family started combing it themselves.

It was Nikki’s distraught boyfriend who finally found the sisters’ bodies, covered in stab wounds and hidden in some bushes. Unforgivably, it would later emerge that two Met officers called to guard the crime scene had casually shared photographs of the murdered women with friends in a WhatsApp group.

But it was the public response when another family’s beloved daughter vanished the following summer that provided the trigger for this book. While Smallman felt deeply for the grieving parents of Sarah Everard, she found it painful to compare the exhaustive media coverage of the search for Sarah with the relatively sparse column inches devoted to her Bibaa and Nikki – who had also disappeared after an innocent night out in London, but who unlike Sarah were respectively Black and mixed race. It’s this question of what and who matters – to the police, the media, and by extension society at large – that forms the heart of this intelligent memoir, which somehow manages to be neither angry nor bitter but suffused with love, empathy and hope.

Though an investigation by the Independent Office of Police Conduct has since found no evidence linking failings in the initial Met response to “stereotyping or biased assumptions” about the sisters’ race or where they lived, their mother is not so easily convinced. “They didn’t care because they looked at Bibaa’s address and thought they knew who she was. A Black woman who lived on a council estate,” she writes in A Better Tomorrow. In fact Bibaa was a senior social worker, responsible and compassionate, the mother of an adored daughter herself. But as her mother points out, it shouldn’t have mattered if she’d been a sex worker or a drug dealer: murder is still murder, a crime to be treated with the utmost seriousness.

From the start Smallman, a former teacher and archdeacon in the Church of England, carefully differentiates in her book between what she calls “the good and the bad within the police”, recognising the efforts of some officers who later earned her trust. She tries hard too to understand what might have gone wrong in the life of the teenager ultimately convicted of killing her daughters, who claimed in court to have sacrificed them in a pact with the devil. And she brings the same nuance to analysing what’s sometimes called Missing White Woman Syndrome, or the media’s long reported tendency to focus on “pretty, white, middle class” victims deemed supposedly more sympathetic to readers.

Accusing people outright of racism, Smallman writes, simply ends up making them defensive: “The best you will get is guilt, an apology and a denial. Nothing changes.” So instead, she explains, she chose to couch her concerns more gently, as questions. Why wasn’t the murder of two sisters considered unusual or important enough to lead the bulletins? Why no public vigil for her daughters, as there had been for Sarah? In the book she stresses that it was never a competition – she isn’t blaming the Everard family for the differences in the way the two cases were treated, or white people in general – and makes clear she holds editors responsible for what makes news, not the reporters she met who seemed genuinely anxious to tell her story. But she also points out how few of those covering the trial of her daughters’ killer were Black themselves.

Where does she get such patience? Religious faith is surely part of the answer: it helped her forgive her daughters’ killer. But perhaps some answers also lie in her own experience as the daughter of a sometimes neglectful and difficult mother she has evidently worked hard to understand. Her father was a Nigerian-born medical student, her mother a Scottish miner’s daughter who already had a child out of wedlock when they met; money was tight, and as a mixed-race couple in 1960s Britain, they met with hostility. As a baby, Mina was fostered out to a stranger for four years – a not uncommon solution then for Nigerian families who couldn’t afford childcare, she writes, but also in her case an unexpected blessing. It was her foster mother who introduced her to the idea of a calm, loving home, and Smallman credits those early foundations with teaching her in turn to become a good mother to Bibaa, Nikki and her surviving daughter Monique. A dysfunctional cycle, it turned out, could be broken after all.

The belief that things can change, that we’re not doomed to repeat the same dismal stories over and over again, has driven her subsequent campaigning on women’s safety and it’s what makes this book an unexpectedly uplifting read. “Things are going to change. I know it,” she writes, confidently. Let’s hope she’s right.