ROME – Whenever a pope appears in public, the focus, in a sense, is always on Peter – that is, on the pontiff as the successor of Peter and therefore chief among the apostles.

When Pope Francis delivers his noontime Angelus address tomorrow, however, he will be sharing the spotlight with a second Peter: Pietro Orlandi, the brother of the famed “Vatican Girl,” who has vowed to be on hand in anticipation of hearing the pontiff say something about his sister’s case on the 40^th anniversary of her disappearance.

June 22 was the actual date upon which 15-year-old Emanuela, the daughter of a minor Vatican employee, vanished in 1983. Over the years, her fate has become something like the Kennedy assassination of Italy, meaning a national obsession as well as a font of conspiracy theories and speculation.

Of late, both the Vatican and the Procurator of Rome, effectively the city’s district attorney, have opened new investigations, and a bill is currently before the Italian senate to launch a parliamentary inquest into the Orlandi case as well as that of Mirella Gregori, another Roman teen who disappeared around the same time.

The Orlandi family’s attorney, Laura Sgrò, has made it clear they’re expecting Francis to address Emanuela’s anniversary tomorrow.

“The hope of the family is that the Holy Father will remember Emanuela with words of hope this coming Sunday during the Angelus,” Sgrò said.

“Emanuela is a citizen of his who’s been missing for 40 years. It would be an important gesture of charity, in a full evangelical spirit, which would put an end to every polemic and reinforce everyone’s will in the search for the truth,” she said.

Pietro Orlandi has been equally clear about what he wants to hear.

“I’m sure that Pope Francis, given his recent desire for clarity about the kidnapping of Emanuela, won’t miss the chance to remember Emanuela and the necessity, after forty years, of truth and justice,” Orlandi said in a June 2 Facebook post.

“We’ll be there to listen to his words,” Orlandi said, inviting ordinary Italians to join him for a sit-in at the Castel Sant’Angelo beginning at 10:00 a.m., before processing down the broad Via della Conciliazione for the Angelus.

Pointedly, he’s asked everyone to arrive holding a picture of Emanuela aloft, to be sure her memory is not lost.

The spotlight on whatever Francis may say comes at a politically delicate moment, given that the Italian senate recently delayed a vote to create a parliamentary investigation amid growing opposition from some legislators who were offended by recent comments from Pietro Orlandi suggesting the late Pope John Paul II might have been involved in his sister’s disappearance.

Many observers were also taken aback when the Vatican’s own prosecutor, Alessandro Diddi, told a June 6 senate hearing that a political probe would amount to “pernicious interference” in his own investigation and that of the Roman procurator.

Orlandi has suggested that the logjam in the Senate is a signal that despite Italy’s pretense of being a secular state, its political life is still characterized by “psychological subjection regarding the Vatican.”

“I don’t understand these delays, they’re not a good sign,” Orlandi said recently. “When you want to do something, you do it and that’s it.

This background makes it especially difficult to know how exactly Pope Francis may thread the needle tomorrow.

On the one hand, as a general rule Francis doesn’t like being painted into a corner. Indeed, many observers have noted over the years that perhaps the most effective way to get Francis not to do something is to insist publicly that he must do it.

For instance, at the very beginning of his papacy there was a scandal surrounding his nominee as the prelate of the Vatican bank, an Italian cleric named Monsignor Battista Ricca. At the time, many Vatican-watchers said out loud that Francis would have to backtrack, removing Ricca from the post.

Ten years later, Ricca remains on the job as the pope’s eyes and ears in the bank.

In addition, Francis is notoriously reluctant to being used politically, which is probably the main reason he still hasn’t returned to Argentina after more than a decade in office. Given the situation in the senate, with a vote on the investigatory commission set for next week, Francis might well be concerned that anything he says might be exploited for political purposes.

Francis was also clearly irritated by Pietro Orlandi’s insinuations about John Paul II, at one point calling them “offensive and baseless,” and might be reluctant to say anything that would lend more fuel to the fire.

On the other hand, Francis also takes his role of the Bishop of Rome seriously, and he also knows the Italian lay of the land extremely well, with a wide network of friends up and down the country well outside the usual clerical circles.

As a result, he knows what a defining national obsession the Orlandi case is in the city of Rome and across Italy, and he also knows that most ordinary Italians believe in their bones that the Vatican has prolonged the suffering of the family over the years by not revealing everything it knows.

Pastorally, he may well feel obliged to try to address the situation, especially having in mind the agony of 93-year-old Maria Orlandi, Emanuela’s mother, who today is in poor health but who says she still believes in “the miracle of embracing Emanuela again.”

It will be interesting to see how the pope balances these considerations Sunday – and, of course, to see how the other Peter in the story reacts.