Laurie R. King never meant to be a mystery writer. Growing up, the 71-year-old California native immersed herself in stacks of science fiction; she assumed that if she ever got a literary career off the ground, that’s what she’d write. Halfway through a draft of her first sci-fi novel in the mid-1980s, however, she hit a wall.

“I realized something as open-ended as sci-fi gave me nothing to build on,” King recalls on a Zoom call from her home in Santa Cruz. “It wasn’t until I rewrote it as a sort of mystery that I knew I could finish the book.”

Mysteries, King says, echoing legions of genre writers and fans, provide a satisfying structure. They promise writers a sandbox of familiar, endlessly remixable tropes, and the opportunity to write about “anything at all” so long as it “works as a story.” Plus, mysteries offer inherent heft: “Even a cozy is about death. If you honor that part of the story, it gives a dimension to the tale that you don’t get if you’re just talking about family drama, or a divorce, or straight-up science fiction.”

In the decades since the mystery genre got King out of a jam, the author has become widely known for her Mary Russell series, which focuses on a young feminist who meets—and eventually marries—Sherlock Holmes in the years after WWI. Russell first appeared in 1994’s The Beekeeper’s Apprentice, and in February, her adventures will continue with The Lantern’s Dance (Bantam), the series’ 18th installment, which marks its 30th anniversary.

The Lantern’s Dance is a bit of a form-breaker for the Russell novels. As always, there’s a mystery to be solved, but the details of the case cut uncommonly close to the private lives of King’s characters. The novel opens with Russell and Holmes arriving in rural France to link up with Holmes’s son, avant-garde artist Damian Adler. (In King’s telling, Holmes has a son with American contralto Irene Adler, who appeared in the 1891 Arthur Conan Doyle story “A Scandal in Bohemia.”)

When Russell and Holmes arrive at Damian’s house, he, his fiancée, and his precocious daughter have all fled to Paris. According to the housekeepers, there was a violent break-in and the intruder left behind a machete. This would be cause for alarm in and of itself, but to make matters worse, a pair of men have been looking for Damian ever since he received chests containing knickknacks from his late great-uncle, the artist Horace Vernet.

From there, Russell and Holmes split up, and so does the narrative. Holmes heads to Paris to fetch his son’s family and ensure the men don’t catch them. Russell, battling a knee injury, stays behind to rifle through the Vernet chests. Among objects of various import (including a zoetrope that gives the book its title), she discovers the coded diary of a young woman named Lakshmi, who was plucked from her home in France to live with an Indian man nearly a century ago. As Russell deciphers Lakshmi’s musings, Holmes helps Damian try to pin down his pursuers, and everything builds to the reveal of explosive family secrets.

Those secrets make up the meat of the The Lantern’s Dance, offering a rare glimpse into the personal history of Holmes, a cultural figure who can seem at once overexposed and underexamined. “One thing that’s fascinating about Arthur Conan Doyle’s work is that he leaves you with a feeling that you know these characters intimately,” King says, “but when you go to actually write down their backstory, you realize that he has not bothered with any details at all.” Her initial aim with the Russell series wasn’t to fill in those gaps—Holmes is a secondary character for the first several entries—but over time, she has allowed herself to engage more fully in what she deems “Sherlockian studies,” even as she remains firm that the books are not Holmes pastiches.

One fertile thread, King says, has been imagining how Holmes might have navigated an England irrevocably transformed by the first world war. Doyle wrote the final Holmes stories in the 1920s, but the chronology never places the detective’s adventures later than the brink of WWI. “I thought that was selling the character short,” King says. “If you have a person like that, whose whole life has been about creatively meeting his challenges, he would not simply say, ‘Oh, things are just too different now, I’m going to retire.’ ”

Instead, he might encounter someone like young Russell, who shares many of his strengths as a detective but also challenges his stoicism and ideas about gender, in a manner not dissimilar from the ways modernists rankled Victorians and Edwardians. As a result, Holmes might grow, fall in love, travel the world, and—as it goes in The Lantern’s Dance—open up about his past.

Such thought experiments have kept King writing about Russell and Holmes for the past 30 years—something she stresses was never the plan. “I know that there are organized writers out there who plan series arcs, but I am not one of those writers,” she says, laughing. Instead, when her publisher tasked her with following up the success of The Beekeeper’s Apprentice, King kept the wind in her sails primarily by juggling other standalones and series, including her novels featuring lesbian San Francisco detective Kate Martinelli, and sending Russell and Holmes all over the globe. As a rule, King only writes about places she’s been—and it’s here that the distance between the author and her characters starts to shrink.

While King insists that Russell is not “her in disguise,” both studied theology, both wear their hair in a crown atop their head, and both married older men with whom they traveled the world. When King was in her mid-20s, she married 55-year-old Noel Quinton King, her former professor whose Anglo-Indian roots shed light on the Lakshmi character in The Lantern’s Dance. Before Noel’s death in 2009, the pair embarked on a series of overseas adventures. While King chose certain Russell settings as excuses to take vacations (for example, 2015’s Dreaming Spies, set in Japan), for the most part, the author is memorializing her own travels with her late husband when Russell and Holmes solve a murder on the Côte d’Azur, or travel to Jerusalem at the request of Holmes’s brother, Mycroft.

When faced with the breadth and success of the Russell series, King responds more with gracious bewilderment than ego. “People have decided to pursue a degree at Oxford because they like Mary Russell,” she says. “Somebody wrote to tell me she’d been clean and sober for a year because of a scene that I’d written. Nobody goes into writing saying, ‘I’m going to write a book that people want to read to their dying mother.’ It’s just an extraordinary privilege to be allowed into people’s lives this way.”

Perhaps it’s because, through the hazy filters of genre convention and Arthur Conan Doyle, she’s been allowing readers into her own life all along.