On May 7, 133 cardinals from around the world will gather for a papal conclave in the Vatican's Sistine Chapel for a secret vote to elect a successor to Pope Francis, who died on April 21.
Behind a cloak of secrecy that would impress the CIA - even their meals are monitored - cardinals in the papal conclave will anoint one among themselves as the new pontiff who will guide the 1.4-billion-member Catholic Church over the next decades.
The 267th pope will determine if the church will continue the reforms started by Francis, or choose a more conventional path.
Cardinals and church staff are sworn to secrecy in all matters relating to the papal conclave, including being sequestered in the Sistine Chapel during voting. No communication with the outside world is permitted. Cardinals are not allowed internet access and can't have smartphones, computers, radios, televisions, or other devices.
It's called a conclave from the Latin term cum clave, meaning "with a key." Here's what happens behind those locked doors:
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The Sistine Chapel was completed in 1481, and its first papal conclave was in 1492. Conclaves have convened consistently at the chapel since 1878.
The chapel's interior is known for its ceiling paintings by Michelangelo and for frescoes painted by Botticelli, Ghirlandaio, Rosselli, and others. More than 5 million tourists visit the chapel every year.
The cardinals are sequestered inside the chapel during voting. They live at the Domus Sanctae Marthae, a guesthouse next to St. Peter's Basilica in Vatican City. It's where Pope Francis took lodging and it's a short walk to the Sistine Chapel.
Under church law, cardinals must gather within 15 to 20 days after the death of a pope to choose a successor. For the papal conclave, the Sistine Chapel is closed to the public and several security precautions are taken to prevent outside influence.
◾The chapel and nearby rooms are electronically swept for cameras, or other surveillance or listening devices.
◾Cardinals and support staff swear on the Bible, under penalty of excommunication, to keep all deliberations secret.
◾Cardinals are secluded during the conclave and are forbidden from any communication with the outside world.
◾A temporary wood floor, or platform, is added to protect the marble floor.
◾Two temporary stoves are installed to burn ballots.
◾Devices that jam electronic signals are installed on the chapel's walls.
◾Wi-Fi access in the Vatican is shut down.
◾The Vatican's Swiss Guards are stationed outside the chapel to prevent unauthorized entry.
Once inside, a cardinal can't leave except for illness or extreme circumstances.
Cardinals eat together during the conclave, but even the menu is restricted. Foods in which messages could be concealed, like pies or chicken, are prohibited.
The Catholic Church has 252 cardinals worldwide. They are the senior officials of the church and are known collectively as the College of Cardinals.
Only cardinals younger than 80 are allowed to vote in a conclave, under a rule called Ingravescentem Aetatem, established by Pope Paul VI in 1970. One cardinal, Cardinal Giovanni Angelo Becciu of Italy, convicted of financial crimes, has said he will not vote. That leaves 135 eligible cardinals.
If a cardinal turns 80 during the conclave, he can still vote.
Two cardinals won't be there because of health issues:
◾Antonio Cañizares Llovera, archbishop of Valencia, Spain.
◾John Njue, archbishop emeritus of Nairobi, Kenya.
That leaves 133 eligible cardinals.
While they are not required to vote for a fellow cardinal - the church's Canon Law says any baptized, unmarried man is eligible - only six non-cardinals have been elected pope in the church's history. The last was Urban VI, in 1378.
On the first day of the conclave, cardinals celebrate Mass in the morning and gather in the Sistine Chapel at 4:30 p.m. They can hold one ballot on the first day.
A set of 12 long wooden tables is placed inside the Sistine Chapel. Cardinals enter the chapel and swear on a Bible to keep deliberations secret.
Those who are not voting are ordered to leave the chapel. The doors are closed.
Each day, all the cardinals choose nine different cardinals by lot:
Here's what happens, according to America: The Jesuit Review and RTVE:
◾The first ballot, the only one of the first day, takes place. At their tables, cardinals use pens to write the names of their candidates on rectangular sheets of paper inscribed with "Elijo como Supremo Pontífice" or "I elect as Supreme Pontiff." They print or disguise their handwriting to maintain secrecy.
◾Cardinals write a candidate's name below the inscription. They fold the paper and carry it to the altar, which has a large urn or chalice with a metal plate on it.
◾They place the paper on the plate, slip the paper inside the urn, and return to their tables.
◾The three scrutineers count and review the ballots, making sure the number of ballots matches the number of voting cardinals.
Names on the ballots are read aloud and recorded. The reviewers check the ballots and recordings of the scrutineers. The work is done in view of all the cardinals.
◾Used ballots are pierced by a threaded needle. When the count is finished, the thread is knotted and the ballots are burned in a special stove installed in the chapel.
◾Chemicals are added to color the smoke black or white. Black smoke indicates no decision. White smoke announces a new pope.
A candidate must have a two-thirds majority - 89 of 133 votes - to be elected pope.
Voting continues on successive days, with two ballots in the morning and two more in the afternoon. If a choice isn't made in three days, voting is suspended for a day of prayer.
Seven more ballots are conducted. If a decision isn't reached, voting is suspended for another day. The seven ballots and one day of suspension are conducted twice more.
If a two-thirds majority isn't reached, the two candidates with the most votes enter runoff elections. The two candidates are not eligible to vote.
However, in the last 12 papal conclaves since 1846, popes have been chosen within three to five days.
The dean of the College of Cardinals asks the newly elected pope if he accepts the election. The new pope then chooses his papal name, one that reflects his heritage, values and history.
The ballots are burned, but this time white smoke billows from the chapel chimney to let the world know of the decision.
The pope enters a chamber in the chapel known as the Room of Tears - named for the emotional reactions of popes who realize their new responsibilities. The room holds papal vestments of three different sizes.
The pope dons the vestments and the cardinals pay homage. Then the pope is taken to the central balcony of St. Peter's Basilica, where a senior cardinal announces "Habemus Papam," the Latin term for "We have a pope" to the waiting crowd.
The pope then addresses the crowd and gives his first blessing.
SOURCE USA TODAY Network reporting and research; Reuters; National Catholic Reporter; OSV News; vatican.va; Georgetown University; therecordnewspaper.org; catholic365.com; aleteia.org; rtve.es; Vatican News; U.S. Conference of Catholic Bishops; America: The Jesuit Review