Rome (CNN) On a sweltering summer's evening in 1983, a 15-year-old girl packed her flute and walked out of her family home inside the vast walls of Vatican City .

The daughter of a prominent Vatican employee -- her father Ercole worked as a clerk in the pontiff's household -- Emanuela would take the bus outside the holy city to classes at Sant'Apollinare basilica.

Her older brother Pietro remembers theirs as a charmed childhood: the Vatican's spectacular gardens were their playground, and Pope John Paul II would stop by and talk to the youngsters having fun on the manicured lawn.

"We thought we were in the safest place in the world," he said, explaining that the city was more like a village, inhabited by a closely-knit group of around six families.

Emanuela Orlandi disappeared in 1983 on her way home from a flute lesson.

But on this particular day, June 22, Emanuela never returned home from her music lesson.

What followed is a mystery that has gripped Italians for more than three decades, inspiring conspiracy theories involving everyone from mobsters to international terrorists and the highest echelons of the Vatican.

Pietro Orlandi , today in his 60s and with a shock of white hair, has relentlessly pursued each lead in a 36-year campaign to reveal what happened to his beloved sister.

Now he hopes to find the answer in a small graveyard, just a few hundred meters from where their mother Maria still lives, inside the city walls.

Pope John Paul II with Emanuela Orlandi (pink sweater, center), and (from right) her brother Pietro, father Ercole, and mother Maria.

Look where the angel is pointing

On Thursday the Vatican began an operation exhuming two tombs inside the Teutonic Cemetery, a pretty courtyard adjacent to the grand Saint Peter's Basilica, which is reserved for the burials of German-speaking Catholics.

Like so much of the Vatican and its institutions, the graveyard is largely hidden from the public, tucked in behind high walls and glimpsed only through ornate metal gates.

The Teutonic Cemetery in Vatican City where two tombs will be exhumed Thursday.

In summer last year, the Orlandi family received the latest in a long list of anonymous tipoffs: A photo of an angel sculpture, and an instruction to "look where the angel is pointing."

The message led the family to two tombs inside the Teutonic Cemetery.

After campaigning from the Orlandis, the Vatican announced earlier this month it would exhume the contents of those tombs.

"Until I don't find Emanuela's body, for me it's a duty to look for her alive," Orlandi told CNN, ahead of the exhumation.

If his sister's remains are there, it is "at least part of the truth," he added. "Then I would like to know the reasons why."

"Even if nothing was to be found, it cannot be the end of the story," he said.

The operation is a complex one, involving Vatican security forces, construction workers and machinery, Vatican spokesman Alessandro Gisotti said last week.

Any bones found during the search would have to undergo laborious DNA analysis, which could take weeks, he added.

Pietro Orlandi, the brother of missing teenager Emanuela Orlandi.

Turning point in investigation

Over the years, the wider investigation into Emanuela's disappearance has been handled by Italian authorities. But the Vatican has said it will handle those parts of the probe that concern its territory -- such as Thursday's exhumations.

The search at the Teutonic Cemetery signals an important turning point in the Vatican's investigation, Orlandi said: "The Vatican has never collaborated with the investigators, with us family members."

"They have always denied the possibility that there may be responsibilities within the Vatican, have always said that they gave everything they had and hid nothing."

Emanuela Orlandi, pictured as a child.

CNN reached out to the Vatican for comment but had not received an answer at the time of publication.

Shortly after Pope Francis assumed the papacy in 2013, Orlandi said he briefly met the new pontiff, who told him: "Emanuela is in heaven."

His words "froze my blood," said Pietro, "to hear a Pope say Emanuela is dead."

But he also hoped for the first time there was a "will to collaborate and get to the truth."

Orlandi said he had since made numerous requests to meet with the pontiff and get a further explanation, but that his attempts came to nothing.

Pietro Orlandi meeting with Pope John Paul II before Emanuela went missing.

Fiorenza Sarzanini, a journalist with Italian newspaper Corriere della Sera, who has followed the case closely for decades, had a different take on the Vatican's apparent change of heart.

"I fear that the Vatican has decided to open the tombs because they know that there is nothing inside," she said. "And this will definitively put an end to the claims of the Orlandi family.

"To satisfy this request by the family -- and in such a public way, with a press release from the Vatican press office -- serves to deflect the suspicious that the Vatican State secretary knows more about the case."

All roads lead to the Vatican

Over the years there have been countless theories about what happened to Emanuela, none of which has ever been proven.

One witness reported seeing a girl who fitted her description getting into a dark green BMW near the music school on the evening she disappeared. The lead was never corroborated.

In the days after Emanuela disappeared, her parents received anonymous phone calls from someone promising her safe return if the Vatican released Mehmet Ali Agca -- a Turkish national who had shot Pope John Paul II in an assassination attempt two years earlier. Again, this lead came to nothing.

Demonstrators gather around Pietro Orlandi during a commemoration ceremony in 2013 marking the 30th anniversary of his sister's disappearance.

Then in 2012 authorities searched the tomb of mobster Enrico "Renatino" De Pedis, who was buried in Sant'Apollinare basilica -- near to where Emanuela was last seen -- after a tip-off suggested it held a clue to her disappearance.

No evidence was found, but questions remain.

"The most incredible thing is that the Vatican has never explained why the mobster, Renatino De Pedis, was buried inside the church of Sant'Apollinare ... an important church in the center of Rome, " said Sanzanini.

Of all the different investigations, there is one "common thread," said Orlandi: "The Vatican."

"Every type of clue has always led to the Vatican," he said.

But "they have always asked the Italian authorities to investigate because according to them (the abduction) happened on Italian soil."

Despite years of fighting for the truth, the Vatican still has a unique place in Orlandi's heart.

"For me it has always been, and perhaps still is, part of my family."

This story has been updated to correct the date the family received the tipoff about the Vatican tombs.