Steiner follows her debut, Missing, Presumed, with Persons Unknown (Random House, July), also starring Det. Insp. Manon Bradshaw, whose adopted son becomes a murder suspect.

Your heroine, Manon, differs from the typical detective because, while she’s devoted to solving cases, she’s blunt and honest about her personal woes, particularly when it comes to being single. How did you develop her character?

To me, Manon is pretty normal, which shows either how twisted I am or how bogus the concept of “normal” is. She’s all there, emotionally. Often fictional detectives have a loner’s quality, which prevents relationships from forming. She’s not one of these. Before writing Missing, Presumed, I’d spent 10 years on a novel about taciturn sheep farmers who couldn’t process emotion let alone articulate it. So creating Manon and being inside her head was tremendous fun—a liberation.

How did you decide to tackle race and racial profiling as plot points?

The fairness of the criminal justice system’s treatment of different racial groups is a mounting issue for most countries. It’s certainly an issue in the U.K., where the police were found to have been institutionally racist in investigating the murder of black teenager Stephen Lawrence. This case was a seminal moment for the British justice system and is very much part of our public consciousness. I have two sons, and I can imagine how heightened my fears for them would be if they were of color. Persons Unknown is based on a real case in London, in which two black teenagers with no prior convictions were wrongly arrested for murder.

Why do you focus so much on family?

I’m more interested in family than in crime. Family is more pivotal, more universal. The complexities of loving and being loved are central to us all. On the other hand, crime—serious, violent crime at least—is rare and outlandish rather than common to our experience. One thing I love about writing crime novels is the freedom to address both, so that my central preoccupation with relationships and the emotional life can sit alongside the puzzle of mystery and the playful laying of clues. It’s a remarkable genre, in that there are really no limits to what you can write about, yet at the same time it demands tremendous structural discipline.

When you wrote Missing, Presumed, did you envision a series?

I set out to write a novel with the ingredients I’d find most delicious as a reader: a plot-driven story with all the riffing about life and relationships that you’d find in a literary novel. I based this on my love of Kate Atkinson’s Jackson Brodie novels. It was only afterwards that the series idea was proposed. Fortunately, I love being in Manon’s company. She has tremendous mileage, and she’ll be back for another case.

Correction: An earlier version of this article incorrectly stated the relationship between two characters in the novel.