In the small of the night, when the mind is open and the defenses are eased, mysteries blossom and conspiracies run wild. In the darkest of hours, Art Bell was a light left on for the lonely, the insomniacs, the Americans searching for answers in a society they believed was spinning out of control.

For more than two decades, Mr. Bell, who was 72 when he died April 13 at his home in Pahrump, Nev., stayed up all night talking to those people on the radio, patiently encouraging them to tell their stories about alien abductions, crop circles, anthrax scares and, as he put it, all things “seen at the edge of vision.” The Nye County, Nev., sheriff’s office said an autopsy will be conducted to determine the cause of death.

At Mr. Bell’s peak in the 1990s, his show, “Coast to Coast AM,” was on more than 400 radio stations. He took calls all night long, alone in the studio he built on his isolated homestead in Pahrump, in the Nevada desert. He punched up the callers himself, unscreened, keeping one line just for those who wanted to talk about what really happened at Area 51, the U.S. government reserve that for decades has been a locus of UFO sightings and purported encounters with alien beings.

Long before fake news became a political topic, Mr. Bell made a good living encouraging Americans to accept the most fantastic and unlikely tales, to believe that we are not alone, to accept that in a world where the pace of life seemed to quicken with every passing year, there were forces from beyond that were trying to tell us something.

In about 40 cities around the country, and in London and Tokyo, Art Bell Chat Clubs met regularly to hear talks by ufologists and by people who described their near-death and past-life experiences. He also had more prominent guests on the show — singers, comics, actors, scientists.

Mr. Bell started his show in 1984 doing a standard-issue political talk program, but he quickly tired of the predictable, emotionally distanced debates over the issues of the day. For Mr. Bell, the questions of the night were infinitely more powerful.

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In 1996, Mr. Bell suggested that the Hale-Bopp comet, then the subject of great popular fascination, was being trailed by a UFO — a theory cited as a possible reason that members of the Heaven’s Gate cult committed mass suicide the next year.

“There is a difference in what people are willing to consider, daytime versus nighttime,” Mr. Bell told The Washington Post in 1998. “It’s dark and you don’t know what’s out there. And the way things are now, there may be something.”

Mr. Bell’s voice was unusually formal, with a classic announcer’s cadence, patient and crystalline, by no means a sleepy sound. What he offered listeners was companionship and a therapeutic acceptance.

The novelist Don DeLillo once wrote that “If you maintain a force in the world that comes into people’s sleep, you are exercising a meaningful power.”

Mr. Bell, who drew an audience of about 10 million listeners a week, saw himself not as an authority, but as a fellow explorer. He wore his gullibility proudly. He believed in possibilities, and he loved the idea that his openness to paranormal events had helped build the nation’s appetite for “Twin Peaks,” “The X-Files” and other expressions of the edges of reality.

He wrote a book, “The Quickening,” spelling out his theory that every aspect of life was “accelerating and changing” so dramatically that the world was hurtling toward doom.

Of course, Mr. Bell had his own experiences that matched those of his callers. On the way home to Pahrump from Las Vegas one summer night, he and his wife, Ramona, were about a mile from home when she blurted, “What the hell is that?”

The couple gazed up. Hovering over the road, they saw an enormous triangular craft, each side about 150 feet long, with two bright lights at each point of the triangle. After a while, the craft floated directly over the Bells. “It was silent,” Mr. Bell recounted. “Dead silent. It did not appear to have an engine.” After a few moments, the craft floated across the valley and out of sight.

On the radio, when he told such stories, he would ask listeners to “try to send mental connective thoughts to ask these beings to show themselves.”

“It really doesn’t matter that much to me if anyone believes me,” Mr. Bell said years later. “Thousands of people seeing the same thing cannot all be wrong.”

And if they were wrong, at least they were wrong together, he said. Whether his show was taken as entertainment or revelation, he believed it was healthier than the other blather on the radio: “Morning shows that compete to find the worst language you can manage to get on the air, the most controversial topics,” he said, dismissively. “Guns! Abortion! I talk about weird stuff. What I do only works at night, only on the radio.”

His politics were all over the map — a self-described libertarian, he opposed abortion, supported same-sex marriage and was skeptical of the science behind global warming. He blamed Richard Nixon for spawning a nation of cynics, supported Barry Goldwater in 1964 and Ross Perot in 1992, came to consider Bill Clinton a great president and said he voted for Barack Obama in 2008.

Mr. Bell had no stomach for haters. He had a white supremacist on as a guest, made him comfortable enough for him to spout racist views, and then Mr. Bell informed the guest that “I am married to a brown-skinned Asian woman.”

Born June 17, 1945, in Jacksonville, N.C., Arthur Bell III grew up with a seven-transistor AM radio tucked under his pillow at night, and when he was supposed to be sleeping, he listened instead to the pioneers of talk radio as they batted around alternative ideas about who really killed John F. Kennedy or how the CIA controlled people’s minds.

Mr. Bell, a Marine brat who said he attended more than 30 high schools as his family moved around, served as a medic for the Air Force in Vietnam, and began his broadcasting work on the military’s station in Okinawa, Japan, where he once stayed on the air as a DJ for 116 hours nonstop, earning an entry in Guinness World Records. (He also held the record for seesawing while broadcasting — 57 hours. Top 40 AM radio DJs did that sort of thing in the 1970s.)

After studying engineering at the University of Maryland, Mr. Bell returned to radio, playing the hits on small stations in New England and California. The work left him feeling empty, and he moved to Las Vegas, where he was working as a cable guy when a radio station asked him to take on a part-time, overnight slot as a talk-show host.

His nightly “Coast to Coast” show ran from 1989 to 2003, and he continued broadcasting on weekends until 2007. He briefly returned with a satellite radio show in 2013 and an online program, “Midnight in the Desert,” in 2015. That show ended after a few months, because, Mr. Bell said, someone had taken to firing a weapon at his Nevada property.

Mr. Bell was married four times; to Sachiko Pontius and Vickie Baker, from whom he was divorced; to Ramona Hayes, who died in 2006; and to Airyn Ruiz, whom he met when she befriended him online after the death of his previous wife. Ruiz was then 22 and living in the Philippines. He is survived by Ruiz and his five children, Vincent Pontius, Lisa Pontius Minei, Arthur Bell IV, Asia Bell and Alexander Bell.

Naturally, Mr. Bell died on Friday the 13th.