The mysterious disappearance of John Pierce began Aug. 24, prosecutors say, when the lawyer missed a hearing for one of the many cases where he is representing a defendant in the Capitol riot investigation. The young associate who took his place said that Pierce had a “conflict.” At the time, no one seemed to give it much mind.

But in the days that followed, Pierce — who is defending more cases connected to the riot than any other lawyer — missed additional hearings and the reasons for his absence started changing.

On Wednesday, his associate told a judge in one case that Pierce had gotten COVID-19 and was in the hospital on a ventilator — but only after telling a prosecutor in another case that Pierce had been in a car accident. That same evening, a different associate told a reporter that Pierce had in fact been hospitalized but was getting care for “dehydration and exhaustion.”

Finally, on Monday — after Pierce had still failed to emerge — the government got involved. Federal prosecutors issued letters to several judges in 17 Capitol riot cases, informing them that no one in the Justice Department had heard from Pierce in a week and that “multiple” phone numbers for his law firm appeared to have been disconnected.

His criminal cases had come to a “standstill,” the prosecutors said, endangering the rights of his clients. If Pierce did not surface soon, they added, something — though it was not clear what — would have to be done.

The New York Times tried to reach Pierce several times by text and phone in recent days, but he did not respond.

Pierce’s unexplained absence was the only latest twist in his outsized role in defending those accused of participating in the Capitol attack. His clients — among them members of the Proud Boys and the Oath Keepers militia — have stood out not only for their number but also for the scorched-earth battle that he has vowed to wage on their behalf.

A self-described pro-Trump populist, Pierce has promised, for example, to force the government to give him video footage of the Capitol for several days before and after Jan. 6 and has said he will demand information about every police officer working at the building that day. He has also vowed to subpoena hostile witnesses like House Speaker Nancy Pelosi, ostensibly to learn what she may have known about security at the Capitol before the attack.

Without citing evidence, Pierce has said he intends to implicate the FBI and the intelligence community by showing that the riot was something like a grand act of entrapment or an inside job. He has often talked about his cases with a conspiratorial zeal, painting himself as something like a lonely legal warrior out to save his clients from an overreaching government.

“I’m like Gerard Butler in ‘300,’” Pierce said in an interview before dropping out of sight, comparing himself to the action star who played a Spartan king. “I’m in the hot gates at Thermopylae, holding the pass against the million-man Persian army.”

While the government has not yet weighed in on the merits on his claims, prosecutors did express concern in their letters filed Monday about the young associate, Ryan Joseph Marshall, who has been standing in for Pierce at the hearings he has missed.

For one thing, Marshall is not a licensed lawyer, prosecutors said, and has taken actions on behalf of clients “that he is not permitted” to take. Moreover, they went on, it remains unclear if and when Marshall will be able to get his law license given that he is under indictment in two criminal cases accusing him of corruption, theft and fraud in Pennsylvania.

Pierce’s situation is not his first encounter with personal and professional setbacks. Last year, his law firm nearly collapsed in a swirl of debts and resignations. Then his most prominent client, Kyle Rittenhouse, the young man charged with murder at a racial justice protest in Wisconsin last year, fired him in a highly public spat that included allegations that a charity arranged for the defense had engaged in financial improprieties.

His work in the Capitol cases began just after the attack when he took several members of the far-right nationalist group the Proud Boys as clients. He has also been hired by L. Brent Bozell IV, the son of a prominent conservative commentator, as well as by a Florida pastor and a Minnesota pub worker.

In recent weeks, however, at least two clients have fired Pierce, complaining that he seemed unresponsive and appeared at times to be unversed in the details of their cases. Last week, the wife of yet another client, Kenneth Harrelson, a member of the Oath Keepers from Florida, sent a letter to her friends and associates, complaining that her husband was having “issues” getting Pierce “to do his job.”

Such complaints have come atop concerns that the sheer number of Pierce’s clients have exposed him to accusations of conflict of interest. He is, for example, representing both James Cusick Jr., the Florida pastor, and Cusick’s son Casey, who are charged with breaching the Capitol with another of his clients, David J. Lesperance, a member of the Cusicks’ church.

In a separate case, Pierce has been hired by another father-and-son pair, Kevin and Nathaniel Tuck, two former Florida police officers who have been charged in an indictment with a Florida Proud Boy he also represents.

Almost eight months after a pro-Trump mob stormed the Capitol, two separate processes have been taking place in Washington. In one, the Justice Department has been filing charges resulting in nearly 600 criminal cases that have only begun to delve into the violence of Jan. 6. In another, conservatives have been waging a war of narratives, playing down the attack as the work of mere tourists or calling it a false-flag operation by the FBI.

Pierce has placed himself at the nexus of these efforts. While he has filed motions and — before his absence — appeared at hearings like any other lawyer, he has also maintained a steady presence on social media and right-wing media outlets, questioning the “Stasi-like tactics” of the FBI, teasing purported revelations about the fatal shooting of Ashli Babbitt inside the Capitol and attacking the investigation as political persecution.

Perhaps the best example of this is his plan to raise a so-called public authority defense for some of his clients, arguing that they cannot be held accountable for the Capitol attack because they were following official U.S. policy.

But Pierce will most likely not point to the role that former President Donald Trump had in whipping up supporters to storm the building. Instead, he has said that he believes that FBI operatives and intelligence personnel, working undercover, incited the crowd to violence. And he has urged other defense lawyers to help him find proof.

All of that, of course, can only come to pass if he returns to court — and the government seems worried that might never happen.

“Unfortunately, it seems that Mr. Pierce may be hospitalized and unable to communicate,” prosecutors wrote Monday, “and it is unclear when Mr. Pierce will recover.”

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