Dick Lehr, the bestselling true crime writer, got his first taste of the criminal justice world at age 25 as a general assignment reporter for the Hartford Courant. “The court reporter was on vacation,” Lehr, 67, says, “so they threw me in to cover for him. I was really green, really rookie. And two things happened: first, I had no idea what was going on. I’d never been in a courthouse in my life, so I felt completely inadequate. And second, I was mesmerized.”

Lehr, who is wearing thin tortoiseshell glasses and seems at ease speaking via Zoom from his home office in Belmont, Mass., has since written eight books. He’s made a name for himself by using true crime stories to explore America’s criminal justice system, revealing its limits and holding up a mirror to society at large in the process.

His latest, White Hot Hate (Mariner, Nov.), is no exception: it’s a high-stakes tale about domestic terrorism that is also a masterwork of investigative journalism. In October 2016, the Department of Justice announced that the FBI had foiled a plot by three militia members who were planning to detonate a bomb at a Kansas apartment complex where hundreds of Somali immigrants lived and worshipped. What didn’t make the headlines was how the FBI had done it. White Hot Hate explores that gripping story.

The character study at the center of White Hot Hate is something Lehr probably couldn’t have pulled off earlier in his career, when he was honing his craft in newsrooms. He’s come a long way since he was that green Courant reporter, and he also remembers the feeling of knowing he had a lot to learn.

“I enrolled in courses just to fast-track my knowledge of criminal justice,” Lehr says. “For the first time I started to see where I wanted to go in my career.”

But where some might have been content to take a few night classes, Lehr went all in: while working full-time at the Courant by day, he pursued a law degree by night. “It took me five years because I would take semesters off,” he recalls. “But a certain inertia took over. I ended up taking the bar because I had the time, but I’ve never really practiced.”

This casual orientation toward his own accomplishments is typical of Lehr, who has added plenty of credentials to his unused law degree. After the Courant, he joined the Boston Globe’s famed investigative journalism unit, Spotlight. There, he worked on a series exposing the abuses of the Massachusetts public disability system; the stories became a finalist for the Pulitzer Prize. At the Globe he met Gerard O’Neill, an editor whose mentorship turned into an out-of-office collaboration. Lehr’s first two books, The Underboss (1989), about the Angiulo crime family, and the bestseller Black Mass (2000), about Whitey Bulger, were both cowritten with O’Neill.

Black Mass was adapted into a 2015 feature film starring Johnny Depp and Benedict Cumberbatch, and won the Edgar Award for Best Fact Crime. Lehr has since gone on to publish six more books, including his first solo-authored work, The Fence (2009); the definitive biography of Bulger, Whitey (2013), which was also written with O’Neill; and Trell (2017), a novel for young adults.

Though crime is still Lehr’s beat as an author and novelist, he doesn’t actually see himself as a true crime writer. “It fits a little bit funny on my shoulders,” he says of his success in the genre. “Having a crime at the center is obviously really helpful for writing purposes. But what’s the bigger thing going on here?”

Lehr has been receiving several true crime pitches each year from strangers, but he’d always turned them down—until spring 2019, when a neighbor rang his doorbell and invited him over to meet a few people who were passing through Boston on their way back to Kansas. “I can’t stop my brain from thinking about a story once it starts,” Lehr says of the conversation that ensued. “Within a day, I wanted it to be my next book.”

One of the men Lehr met at his neighbor’s house was Dan Day, a white working-class Kansan who had infiltrated the bombers’ plot. Day posed as their accomplice for eight months while secretly taping his conversations as an informant for the FBI.

White Hot Hate draws on thousands of pages of court testimony and evidence, including Day’s tapes, to tell the story of how he went from being a skeptical potential militia recruit to becoming the FBI’s inside man. Day risked his life for his Somali neighbors, who, at the time, were strangers to him. His story is one of unlikely heroism and fundamental human decency.

To tell that tale, Lehr drew on a lesson he’d learned as a journalist: good storytelling is a marathon not a sprint. “You’re going to burn out in a week at Spotlight if you don’t chill,” he remembers O’Neill telling him. So Lehr committed himself to the hard work of earning Day’s trust. He flew to Kansas for their first interview. “It was the end of the summer, and we met in a park,” he remembers. “He was in shutdown mode. For two years he had been, in effect, hermetically sealed by the government. I needed him to break out of that mode.”

Eventually, Day opened up. Lehr knew he had turned a corner when Day invited him to go target shooting. “Without hesitation, I said sure,” Lehr says, even though he had never fired a gun before. “He and his son got in their truck and took me out past Holcomb, Kans., by the Clutter farmhouse from In Cold Blood, near where his sister lived, and we were set up in fields all afternoon target shooting.”

The excursion was also a valuable chance for Lehr to see what makes his subject tick. “I got a sense of his love of guns, but also his obsession with gun safety.” It was an obsession that he learned was part of Day’s ethical compass.

Day’s trust allowed Lehr to write a book that is nuanced in its approach to a divisive and urgent topic. Lehr’s editor at Mariner, Rakia Clark, says that the story of the domestic terror plot that Day helped avert felt even more important after the insurrection of Jan. 6, 2021. “It was, ‘Okay: how quickly can you finish the manuscript?’ ” she explains. “How quickly can I edit? How quickly can we get it into copyediting?”

Fortunately, Lehr’s decades of experience as a journalist made this easier. “The best thing you can do as an editor with a writer like Dick is get out of the damn way,” Clark says. “Dick is a pro. My goal was to be the wind at his back.”

Now that his work on White Hot Hate is done, Lehr has had a chance to step back. He’s been reading omnivorously, and, as a professor of journalism at Boston University, he has been thinking about the challenges his students will face as reporters. “There’s so much conflict reporting,” Lehr observes—something that wasn’t true when he was starting out.

But Lehr is also looking forward. He’s been tapped to produce and host a new true crime podcast, a partnership between the Boston Globe and Boston radio station WBUR, about an unsolved murder that he’s covered over the years. The subject matter might be familiar, but the format is new territory for Lehr, and he couldn’t be more excited. “It stretches me in a new direction,” he says. “I like that.”

Lehr admits he has a lot to learn, but you can bet he won’t stop until he’s gotten it right.

Andy Kifer cowrote Mutualism: Building the Next Economy from the Ground Up (Random House) with Sara Horowitz and is working on a book of narrative nonfiction about America’s secret cities.