Daniel Harper is the co-host of what might be the most important podcast countering the white nationalist movement today.

It’s called I Don’t Speak German, and since launching in January it has helped lead people back from the brink of radicalization, drawn plaudits from researchers of violent extremism, and attracted an audience of thousands of regular listeners.

But for Harper, it’s also come at a personal cost. He routinely has been harassed online by the very subjects he discusses, and he constantly has to think about the safety of himself and his family.

Those concerns became clearer last month when federal authorities rolled out criminal charges against Jarrett William Smith, a U.S. Army soldier in Kansas who was active in the online white nationalist community that refers to itself as “Terrorgram.”

Some of the allegations against Smith immediately drew major headlines. The feds said he wanted to blow up the headquarters of a major news network, gave out instructions online about how to build bombs, and planned to travel to Ukraine to join up with a far-right militant group.

But there was another allegation that got significantly less attention: The soldier allegedly also gave out instructions on how to burn down the house of a man described in court records only by the initials D.H.

That man was Daniel Harper, who spoke to The Daily Beast about being on the receiving end of a threat by a self-proclaimed satanic neo-Nazi who also happens to be in the military.

“I want to be really clear on this,” Harper said. “I don't think this guy was going to show up at my house and burn it down.”

However, he added, “it’s absolutely within the realm of plausibility that some 19-year-old dipshit’s going to decide to do something” because of what Smith was posting online.

Harper would know. He’s been obsessively tracking the racist right for the past three years and has proven to be something of a savant when it comes to understanding the figures and dynamics of the movement.

His quest began in 2016 on something of a lark. He’d been observing the resurgence of white nationalism in America but was curious to know more about it.

Along the way, Harper saw a reference online to a racist alt-right podcast, which at the time was called Fash the Nation. Already an avid podcast listener, he decided to add it to his rotation. He figured it might become a tool for him to be able to explain the movement to his friends.

“It was really this idle curiosity, and I just wanted to do something in the face of this Trump presidency and this new era that we were obviously in,” Harper said.

He quickly found more racist podcasts along with racist YouTube livestreams to consume. After just a few months, it began to dawn on him that he was developing a base of knowledge that few other people had.

Yes, he was listening to white nationalist propaganda, but it felt like he was eavesdropping on some kind of secretive subculture that he, a devoted leftist and anti-racist, wasn’t supposed to be hearing.

When the deadly “Unite the Right” rally happened in Charlottesville, Virginia, in August 2017, Harper decided it was time to turn this into a serious research project. He began downloading, archiving, and tracking as much racist audio content as he could.

It wasn’t quite clear what he was going to do with all of it. He already had a day job, and this was something he was doing in his free time. And he realized he was listening to 30 to 40 hours of racist content per week.

“I was off on my own forever,” Harper said. “It often felt like I was like a deep-sea diver... just in this murky world of awfulness.”

Then a friend, Jack Graham, suggested they turn it into a podcast of their own. The idea for the format was simple: Graham would ask Harper about certain topics, and Harper would rattle off his knowledge of them with a mix of horror and humor. Occasionally, they would have guests on to talk about specific groups or movements.

The pair launched I Don’t Speak German at the start of this year and have already turned out 33 episodes, with more on the way.

The episodes often focus on the follies of the racist right. The white nationalist movement, despite its body count and frequent glorification of genocide, has often been plagued by infighting and incompetence—something Harper and Graham are more than willing to highlight.

The pair talked at length (Episode 8) about the bizarre love triangle and violence that tore apart the Traditionalist Worker Party, a neo-Nazi group that took part in the violence in Charlottesville. And they can’t seem to stop talking, in whatever episode, about the absurdist troubles of “Crying Nazi” Christopher Cantwell.

“So much of what I try to get across is to emphasize the humanity in these people, without shying away from how terrible the things that they say are,” Harper said.

That approach, along with Harper’s encyclopedic knowledge, has driven people to the podcast.

David Neiwert, a veteran journalist and author who’s covered the racist right for decades and who was a guest on a July episode of I Don’t Speak German, told The Daily Beast the show strikes just the right tone.

“Daniel and his cohorts do terrific work confronting the disinformation deluge we're all contending with these days, and they do it with wit and humility, which are essential to this kind of work,” Neiwert said. “Their podcast is kind of a survival guide for the new age of agitprop, and I love listening to it.”

While Harper said the majority of the audience sits on the political left, he also knows that there are a number of white nationalists who listen to what he and Graham talk about. Sometimes those people post vicious comments about him online. Sometimes they email him.

And sometimes, he said, those emails will surprise him.

One email he received this year, he said, was from someone who told him they were in a “dark head space” and on the path to becoming a mass shooter. But listening to the show, the emailer said, helped walk them back from the edge.

“It's humbling in this weird way,” Harper said. Mostly because it’s not the kind of response he expected when he started the podcast. “That's a great thing, but it's certainly not where my head space is when I'm recording it.”

Jesse Morton can testify to the positive impact of I Don’t Speak German. He’s a former jihadist propagandist who now serves as the head of Light Upon Light, an organization that works to combat hate and extremism.

A research consultant for the organization, Samantha Kutner, has been a guest of the podcast, talking about her study of the far-right Proud Boys.

“Her episode alone got four or five productive engagements and interventions with far right-wing extremists,” Morton told The Daily Beast.

One person who reached out to Light Upon Light because of the podcast said he was thinking about being a mass shooter and wanted Morton’s group to convince him otherwise.

“He came from the podcast,” Morton said. “He's an avid listener, and we continue to have engagements with this individual onto today where we've walked him down to a point of disengagement.”

Morton, too, credited the show’s blend of information and humor.

“That's the way to cover it. In the way that society deals with extremism in general, terrorism just evokes a very serious mental state of shock and awe,” Morton said. “There's a way to cover far right-wing extremism and terrorism with humor that can be really provocative.”

But as the case against Jarrett William Smith shows, covering extremists has its risks.

In early September, Harper and his co-host released a pair of episodes that focused on the adherents of an obscure neo-Nazi author named James Mason. A book Mason wrote has become a bible of sorts for terroristic neo-Nazi groups like Atomwaffen Division, and it has helped spawn a new wave of so-called accelerationists—people who believe societal collapse is the quickest way to create an all-white ethnostate.

Many of those adherents flocked to Telegram, the encrypted messaging app, in recent months after getting booted from other social media platforms. And they’ve created their own enclave there, which they refer to as “Terrorgram.”

It was there, in the Terrorgram community, that the threats against Harper took shape.

On Sept. 11, an anonymous post appeared on one of the Terrorgram channels, telling people to send Harper “fan mail” at his address in Michigan.

The following day, the same channel published a video from someone who drove by the address and filmed the house. “Howdy, antifascist activist Daniel Harper,” the text of the post read. “Nice place you've got there.”

The posts set off a wave of chatter on Telegram. In the midst of it was a user who went by the handle “Anti-Kosmik 2182,” who chimed in with his thoughts about what to do about Harper.

“ I’m not saying do anything illegal, but I am saying it would be a real shame if all he has went up in literal flames. ” — Anti-Kosmik 2182

“Ditch the car somewhere a few blocks away, take back alleys, trails in the woods, etc., and then come up on the house wearing a mask,” he wrote. “I’m not saying do anything illegal, but I am saying it would be a real shame if all he has went up in literal flames.”

In court records, the FBI later said that “Anti-Kosmik 2182” was Smith, an infantry soldier stationed at Fort Riley, Kansas. The bureau also revealed that it had an undercover agent on Telegram who was interacting with Smith around the same time.

Smith was arrested on Sept. 23 and charged with two counts of distributing information about weapons of mass destruction and a third count of sending a threatening communication over state lines.

Harper said he’s used to harassment online, but the threat was something new.

“If they just want to make fun of my man boobs, it's like, ‘Whatever,’” he said, laughing. “The threats from people who actually seem to be at least tangentially connected to literal terrorists? That worries me a lot more.”

But it’s not going to stop him from podcasting or possibly even doing more with his research. He said he plans to write a book based on his experiences over the past three years.

There’s a lot of material to work with, and the podcast is just the beginning.