Jamal Khashoggi in Davos, Switzerland, in 2011. (Virginia Mayo/AP)

JAMAL KHASHOGGI, a journalist who has turned a trenchant and questioning eye on the leadership of his country, Saudi Arabia, entered the kingdom’s consulate in Istanbul on Tuesday to take care of what should have been routine paperwork. Saudi Arabia says he then left. His fiancee, waiting for him, says he did not, and he cannot be found. Turkey says it has seen no sign that he left the building. Mr. Khashoggi, a contributor to The Post’s Global Opinions section, appears to have disappeared, and we are worried.

Mr. Khashoggi is not just any commentator. Over a long career, he has had close contact with Saudi royalty and knows more than most about how they think and function. His criticism, voiced over the past year, most surely rankles Mohammed bin Salman, who was elevated to crown prince last year and has carried out a wide-ranging campaign to silence dissent while trying to modernize the kingdom. Among those in his prisons for political speech are clerics, bloggers, journalists and activists. He imprisoned women who agitated for the right to drive, a right that was granted even as they were punished.

Mr. Khashoggi saw the writing on the wall. After Donald Trump’s election, Mr. Khashoggi remarked at an event at the Washington Institute for Near East Policy that the kingdom was rightfully nervous about a Trump presidency. This comment apparently angered the Saudi leadership, which hoped to ingratiate itself with the new president. Mr. Khashoggi was told to stop writing and using Twitter. Seeing so many others imprisoned for their views, he decided to leave the country. He wrote for The Post in September 2017, “I have left my home, my family and my job, and I am raising my voice. To do otherwise would betray those who languish in prison. I can speak when so many cannot.”

He continued writing columns for The Post after that. He wrote in February that the crown prince’s restrictions on free speech had “sucked the oxygen from the once-limited but present public square. You can read, of course, but just think twice about sharing or liking whatever isn’t fully in line with the official government groupthink.” In June, he praised the crown prince for the decision to let women drive but urged him to free the female activists. In August, he admonished Saudi leadership that it was a mistake to pick a fight with Canada over human rights after the Canadians spoke out against abuses in the kingdom.

The crown prince has been all over the United States preaching his vision of a more modern Saudi society, breaking out of the stale old religious codes and practices, opening up to foreign entertainment and investment. If he is truly committed to this, he will welcome constructive criticism from patriots such as Mr. Khashoggi. And he will do everything in his power to ensure that Mr. Khashoggi is free and able to continue his work.