Salman bin Abdulaziz bin Salman had all the privileges of a Saudi prince. Wealthy and urbane, he traveled the world, moving between properties in France and Saudi Arabia. He attended the elite Sorbonne University in Paris — and is fluent in Arabic, English and French.

But on the night of January 4, 2018, Prince Salman’s world came crashing down.

Not all the facts are clear, but friends say the prince was at his home near Riyadh when he received a summons to the Qasr al Hukm palace. When he arrived at the palace, an argument quickly became a fracas.

Friends of Prince Salman say Saud al Qahtani, who was then a close adviser to Crown Prince Mohammed bin Salman, was present.

Al Qahtani was relieved of his position later in 2018 amid allegations that he was involved with the murder of Saudi journalist Jamal Khashoggi in Istanbul. In November, prosecutors said he was under investigation and was barred from leaving the kingdom.

Friends of Prince Salman say he was detained and taken to the maximum security Ha’ir prison outside Riyadh.

The only official comment at the time came from prosecutors who said 11 princes had been detained after they had gathered at a royal palace in Riyadh in a protest against the government suspending payment of their utility bills.

“Despite being informed that their demands were not lawful, the 11 princes refused to leave the area, disrupting public peace and order. Members of a security services stepped in to restore order and the princes were arrested,” the prosecutors statement said.

Whatever caused the dispute, human rights groups say Prince Salman’s imprisonment illustrates a pattern that’s emerged in Saudi Arabia over the last two years: one of arbitrary detention where charges are rarely brought and where individuals are detained if they seek redress for a friend or family member who is under arrest.

Two days after Prince Salman was detained, his father, Prince Abdulaziz bin Salman bin Mohammad Al Saud, was also arrested — after involving international lawyers in his son’s case.

Saudi authorities have not responded to repeated requests from CNN for information about the two men. Neither has been charged, according to associates.

Prince Salman is not a senior royal, but he is married to a daughter of the late King Abdullah.

For the first four months of his detention, Prince Salman was allowed no communication with friends or family. Friends say he was then allowed two telephone calls a week. After more than a year in detention, he and his father were moved to a different, guarded compound where conditions were less sparse. They were recently permitted visits from family members.

The reasons for Prince Salman’s arrest 15 months ago are still unclear. Those close to him say he had lobbied for the release of a cousin who had been detained as part of what Crown Prince Mohammed bin Salman described as an anti-corruption purge that began in November 2017.

The cousin was Prince Turki bin Mohammed bin Saud al Kabeer. Prince Turki was an adviser to the King who had worked at the Foreign Ministry for more than 30 years. Sources say Prince Turki had been privately critical of the Crown Prince. He was eventually released three months after being detained.

Some friends of Prince Salman believe he may also have angered the Royal Court by meeting a prominent US Democratic congressman, Adam Schiff, along with a major donor to Hillary Clinton’s presidential campaign, Andy Khawaja, weeks before the 2016 US election. The meeting was in Beverly Hills on October 16, 2016.

They say the meeting had no political agenda but may have been perceived in Riyadh as counter to Saudi Arabia’s unspoken preference for Donald Trump over Clinton.

Schiff’s office told CNN that the congressman doesn’t recall any specifics from the discussion but assumes they would have talked about Middle East policy and Saudi Arabia generally.

At the beginning of this month, CNN asked Saudi authorities why the prince and his father were detained, whether they have been charged and whether they have been allowed access to family and lawyers. Despite several requests for information, CNN received no response.

The European Parliament has also asked for information about the case. Pier Antonio Panzeri, who leads the subcommittee on human rights, first raised Prince Salman’s detention with the Saudi ambassador in Brussels in February and this week wrote to the Crown Prince appealing for Prince Salman’s release. He told CNN he has received no response to his inquiries.

Widespread arrests

Prince Salman and his father are among dozens of prominent Saudis — including members of the royal family, clerics, intellectuals and human rights advocates — who are being held without charge, according to their families and human rights groups. CNN has reported that they include a dual US-Saudi citizen, Dr. Walid Fitaihi. His family believes he has been tortured, a source told CNN.

This month, several more intellectuals and journalists were arrested, apparently for seeking to publicize the cases of detained women’s activists. The State Department confirmed last week that among them is Salah Al-Haidar, a dual U.S.-Saudi national who has homes in Virginia and Riyadh. His mother is the prominent women’s rights activists Aziza al-Yousef, who recently was temporarily released from prison.

The rights group Human Rights Watch (HRW) has also highlighted the continued detention of other more prominent members of the royal family “outside any legal process” as part of the anti-corruption drive that was launched in November 2017. They include Prince Turki bin Abdullah, the former governor of Riyadh.

Among others still held without charge are former Economy Minister Adel al Fakeih, who had been an influential figure in Saudi Arabia’s modernization plan.

HRW said in February that “Saudi authorities should immediately clarify whether those in detention face charges in connection with the anti-corruption campaign or for other recognizable criminal activity, and if not, the authorities should release them immediately.”

The anti-corruption campaign was formally ended in January, when a royal court statement said that the anti-corruption committee, led by the Crown Prince, had “concluded its tasks” after summoning 381 people to give evidence. It said 64 cases remained unsettled. It’s unclear where or under what conditions those 64 individuals are being held.