But Kennedy’s hesitancy faded by the end of the decade, and he was heartened by early polls that showed Democratic voters would favor him over Carter in a presidential primary battle. “He was running for president because he really believed President Carter was not addressing issues that were important,” says Stuart Shapiro, a former Kennedy senior staffer. “That’s why, after much soul-searching, he decided to take on a sitting president.”

Running for the country’s highest office, though, increased the odds that Kennedy could become a target for some deranged would-be assassin who might lurk, anonymous and undetected, at a busy rally. It was no idle threat. In March 1980, a tipster in Charlotte, North Carolina, contacted the police after overhearing a group of men in a movie theater bragging that they planned to assassinate Kennedy in Pittsburgh, with some stolen M-16 rifles. A campaign volunteer in Trenton, New Jersey, received a phone call from a man who vowed to gun down the senator when he visited the city in May.

Aside from blurting, “They’re going to shoot my ass off the way they shot Bobby,” while on a congressional flight back from Alaska, Kennedy shied away from sharing his assassination fears with aides or family members. Instead, he tried to project an air of invincibility, or at least indifference. “I remember being in Iowa, and when we’d first go out there, the Secret Service would create this huge space between him and the crowd,” Shrum tells me. “And he hated it. So he started working the rope line again.”

Privately, Kennedy sought out his physician and political adviser, Larry Horowitz, and handed him something important. “It was a letter my father had written to me at the start of his presidential campaign, in case he was assassinated,” Patrick Kennedy, his youngest son, recalled in his 2015 book, A Common Struggle: A Personal Journey Through the Past and Future of Mental Illness and Addiction. “In it, he talked about how much he loved me, and how I had given him so much love. He said he would never forget the times we went fishing and sailing.” Kennedy took to calling Patrick from the road every night—his way of letting his adolescent son know nothing bad had happened.

The informant who contacted the FBI in 1980 said he’d received a phone call, too, on October 20. The caller had identified himself as LaVey, the informant claimed, and disclosed that he wanted the man’s help with a plan to murder Ted Kennedy.

The FBI and the Secret Service knew two things for certain: LaVey still lived in San Francisco, and they needed to get a handle on the case—and quick.

Investigators didn’t have to contend with Twitter or Facebook, digital echo chambers that decades later would make political discourse more toxic and create ideal delivery systems for trolls to share threats. But they also had fewer tools at their disposal. “We didn’t have all of the modern vehicles of communication or detection that you have today,” says William H. Webster, who was the director of the FBI from 1978 to 1987. “Investigations involved a lot of interviews and personal contacts.”

The FBI’s San Francisco office pulled records it had on LaVey dating back to the mid-’70s, when a tipster told the bureau that LaVey had purchased handguns, a shotgun and a rifle. Other files showed that LaVey had once supposedly been “interested” in joining the National Socialist White People’s Party, which had been known, in an earlier incarnation, as the American Nazi Party.

LaVey had no arrest history, but he’d been linked to a tragedy once before. His relationship with Mansfield had reportedly ended with LaVey’s putting a curse on Sam Brody, the actress’ attorney and boyfriend, promising that he’d die in a car crash. In 1967, not long after the hex was supposedly cast, Brody and Mansfield were killed in a wreck on a highway near New Orleans. The improbable implication—that LaVey inadvertently caused Mansfield’s death—persisted long enough to fuel a 2017 documentary, Mansfield 66/67. (In truth, LaVey did not have magical powers.)

Anton LaVey | AP

The Chicago informant—whose identity is still being kept secret by the FBI—told agents that he’d had dinner once before with LaVey, who explained to him the Church of Satan’s beliefs. When they supposedly reconnected by phone in 1980, LaVey told the man that he owed the high priest a favor. His alleged instructions were simple: In a week or so, the informant would receive a package, and he must ferry it to a mob boss on the South Side of Chicago; the mob would, in turn, take out Kennedy. After the phone call, the informant was visited by a member of the Church of Satan, whose purpose “was specifically to discuss the satanic cult and the plot against Senator Kennedy,” according to FBI records.

There was more. The informant told the FBI that LaVey was going to fly to Chicago on October 27, carrying with him eight kilograms of hashish and an unknown amount of cash. Was this another piece of the puzzle to the assassination plot? Taking no chances, the FBI, Secret Service and DEA sent agents to O’Hare International Airport to intercept flights from San Francisco and apprehend LaVey, like something out of Steven Spielberg’s Catch Me If You Can. But there was no sign of him at the airport. An attempt at monitoring a phone call to LaVey also failed.

The Secret Service had polygraphed the informant prior to the fruitless airport search. “Results were inconclusive,” investigators noted, “due to use of cocaine.” They pressed on. They had to find LaVey. “I was a young agent when President Kennedy was killed, and [investigated] some leads on the case,” says Francis Mullen, who had risen to executive assistant director of the FBI by 1980. “When Bobby was assassinated, I was in Los Angeles, coordinating some of the leads on that case. If a threat had come in on the third brother, we’d have to take it seriously.”

Two days after the search at O’Hare came up empty, agents flew to San Francisco, and made their way to the Black House. A woman who answered LaVey’s door told them that he was traveling, and wouldn’t be back for several days. Another whiff. The investigators warned her they had information that suggested “an attempt may be made on LaVey’s life,” according to the records. They encouraged the woman to get a hold of LaVey and urge him to make himself available for an interview.

Publicity photograph of Anton LaVey

Kennedy’s Secret Service detail was kept in the loop about the potential threat, but it’s unclear whether the senator was aware of the investigation. “I spent a lot of time with him privately, and I don’t ever recall hearing about that one,” Shapiro says. “But I can tell you there were times when the Secret Service wanted him to wear a bulletproof vest.” The informant, meanwhile, had been polygraphed again, and was facing increased scrutiny. The FBI began to notice inconsistencies in his account. Were the agencies being played?

Investigators returned to the Black House a second time, on Halloween. And this time, when the door opened, they came face-to-face with LaVey. For years, he had enjoyed toying with people’s imaginations, blurring the lines between performance and something darker. But now he was faced with no-nonsense federal agents, and they weren’t in the mood to play around.

For a man who referred to himself as the “Black Pope,” the notoriety of being linked to an FBI investigation might have been a welcome development when he was first seeking attention for his church. This older version of LaVey, though, decided to come right out with it: He had nothing to do with any assassination plot.

“LaVey advised that of any political official, he has the highest regard for Senator Kennedy and his family,” according to the FBI records. And LaVey could sympathize with the threats that Kennedy often received; he told the agents that he had been the victim of physical and verbal attacks because of his position in the Church of Satan.

LaVey checked his recent phone messages, and noticed that he’d received calls from the Chicago area on October 23 and October 27. But he told the agents that he didn’t know the identity of the caller and hadn’t tried dialing the number that had been left for him.

And then LaVey shared some surprising news with the agents: His role as the head of the church was all a charade. Most of the church’s followers, he said, were “fanatics, cultists, and weirdos,” the records show. “[H]is interest in the Church of Satan is strictly from a monetary point of view,” the agents noted, “and spends most of his time furnishing interviews, writing material, and lately has become interested in photography.”