ROME—Pietro Orlandi is 100 percent sure that the Vatican knows a lot more than it says about what happened to his sister when she disappeared more than 35 years ago. And he is sure that the Roman Catholic clergy want to keep that secret, like so many others.

Emanuela Orlandi, who lived inside Vatican City where her father worked for the Vatican Bank, disappeared June 22, 1983. She was last seen in front of Sant' Apollinare, an Opus Dei church near Piazza Navona in Rome. She had just finished a flute lesson. She was 15 years old.

Now the Orlandi family has received an anonymous tip that could start the mystery unraveling, and it comes at a time when extraordinary allegations about sexual slavery elsewhere within the church have been acknowledged as true, including by Pope Francis.

The tip about Emanuela came in the form of a brief letter sent to the Orlandi lawyer from inside the Vatican, accompanied by a photograph. It showed a stone angel at an unmarked tomb in the Teutonic Cemetery, which lies inside the Vatican walls. The cemetery is not accessible to the general public, but someone keeps a red votive candle lit at this tomb—only at this tomb— and there are always fresh flowers in a vase. The only thing engraved on it is a marble scroll the angel holds: Requiescat in Pace, it says. Rest in Peace.

“I wish so much that this whole story was a hoax. I really wish Emanuela was not here,” Orlandi told The Daily Beast. He has spent the last 35 years searching every false lead that might lead to the truth about what happened to his sister, and he is weary. “I do it for my mother, for my sisters, for my father who is dead. I do it for me, of course. Even if it means I am going to be met with the pain, with the doors slammed in the face, with disappointments.”

Orlandi’s family now wants the pope to grant permission to exhume whomever or whatever lies in the mysteriously tended tomb, which is reported to have been opened “at least once” in the last few decades. According to Italy's Corriere Della Sera newspaper, cement work shows it has been re-sealed.

The Vatican spokesman said in a statement that the Holy See is “studying” the matter and will soon decide whether to honor the request.

If Emanuela’s body is buried inside the Holy See, it would give oxygen to one of the most sensational theories about her disappearance: that she was kept as a Vatican sex slave.

In a general sense, given revelations about what has gone on elsewhere in the Catholic Church, this allegation is not so wildly sensational as it once sounded. Allegations of widespread clerical sex abuse of young women and nuns, including the pope's admission earlier this year that many were treated as sex slaves do nothing to quiet the whispers.

New norms introduced by Francis in recent months that focus on sex abuse activity inside Vatican City also raise eyebrows. Over the past several years, the Vatican has been pressured to admit its own judiciary has investigated cases of possession of child pornography by clerics behind the walls of the Vatican.

A 2014 report by Torrentfreak, a site that specializes in Web user statistics, tracked online pornography downloaded from Vatican IPs. One of the titles in German translates as "BDSM Slave Punishment in the Dark Hobby Cellar - Teen Bondage."

The Vatican's chief exorcist Father Gabriele Amorth, who died in 2012, was the first to endorse the theory that Emanuela’s disappearance was sexual in nature.

“Parties were organized in which a gendarme of the Holy See was involved as a recruiter of women,” said Amorth, who was a great confidant of retired Pope Emeritus Benedict XVI. “I believe Emanuela is a victim of that racket. ... I have reason to believe that it was a case of sexual exploitation resulting in murder shortly after the disappearance, and [then] concealment of the corpse.”

In 2016, Monsignor Simeone Duca, an archivist with the Vatican, backed up the exorcist’s claims, citing “credible information” that “certain factions” inside the Vatican’s diplomatic corps were involved in procuring young adolescent girls for sexual slavery. He, too, said he believed that Orlandi was abducted for that purpose and later killed when her innocence was no longer amusing.

Since no body has been found, there is no credible proof that she is eitehr dead or alive—but there are plenty of suggestions that she could be one or the other.

In 2017, Italian journalist Emiliano Fittipaldi was given a leaked Vatican document that was said to list expenses for the care of Orlandi abroad, which included room and board and gynecological examinations. The Vatican vehemently denied the authenticity of the document, calling it a “false and ridiculous reconstruction.”

Other conspiracy theories run the gamut, from Turkish militants tied to the assassination attempt against Pope John Paul II to a local mobster who headed a Roman gang called the Band of Magliana. The mobster’s grave was pried open in 2012 inside the Opus Dei church near where Orlandi disappeared. There were plenty of bones of other people buried with him, weirdly enough, but none were the missing girl’s.

Orlandi’s lawyer Laura Sgrò says that the family was prepared to send a letter to the Vatican’s secretary of state last October to ask that he clarify who is buried in the mysterious angel’s tomb after someone started dropping anonymous hints about the graveyard.

The Teutonic Cemetery, where Germans with ties to the Holy See are buried, was a favorite spot of the retired Pope Benedict XVI, who gave mass at the adjoining chapel once a week before he was elected pope, so they hoped that he also might help shed light on the matter.

But then last Halloween, as it happens, bones were found under the pavement of a Vatican-owned property in Rome during renovations. As is often the case when such mysteries unfold under the shadow of the Vatican, thoughts immediately turned to Orlandi. But it turned out those bones were 200 years old.

It may take weeks—or months, or even years—for the Vatican to respond to the Orlandi family’s latest request. “We've been asking for collaboration from the Vatican for 35 years,” says the missing girl’s brother.

“Collaboration that has never been. This time we are asking again. Even collaboration that is discreet, just to understand. Just to remove this doubt.”