THE DISAPPEARANCE of Jamal Khashoggi remained a mystery on Monday, but unlike many mysteries, it is one that could easily be solved. The Saudi journalist and Post Global Opinions columnist walked into the Saudi Consulate in Istanbul at about 1:30 p.m. last Tuesday, Oct. 2, and has not been seen or heard from since. Turkish government sources are saying he was murdered inside the consulate; Saudi officials are calling that allegation “baseless and ridiculous.” They contend that Mr. Khashoggi left the consulate shortly after he arrived.

If either account is correct, there should be tangible evidence — videos, travel logs and other documents — to back it up. Such evidence should be immediately released. Any delay only magnifies the suffering of Mr. Khashoggi’s family, including the fiancee who waited for him in vain outside the consulate. It compounds the crime of those responsible for his disappearance, who will not succeed in deflecting questions through stonewalling.

We know that security cameras monitored the streets around the Saudi Consulate. The kingdom’s ambassador in Washington, Prince Khalid bin Salman, told The Post the consulate’s cameras were not recording. But footage from Turkish cameras is believed to be available. Turkish sources have said there are images of Mr. Khashoggi leaving the consulate on a previous visit on Sept. 28 but none from Oct. 2. Formal confirmation of that result from Turkish authorities would support the account of Mr. Khashoggi’s fiancee, Hatice Cengiz, who says she waited for him outside the mission until after midnight but never saw him. It would strongly indicate that the Saudi account is false.

Turkish officials also have disseminated a report that 15 Saudi nationals flew into Istanbul on the day of Mr. Khashoggi’s disappearance and were inside the consulate when Mr. Khashoggi disappeared. A private Turkish news agency, DHA, said the group arrived on two Gulfstreams belonging to a Riyadh-based company and that they landed at Ataturk Airport. If that is true, there should be records of the planes landing, and perhaps passenger manifests and passport records, along with more video from the airport and consulate. Its release would belie Saudi claims that no such delegation visited.

Mr. Khashoggi visited the consulate to obtain paperwork certifying a previous divorce. If consular officials, who had told him on Sept. 28 to return on Oct. 2 in order to complete that business, supplied him with the document he requested, they should have records demonstrating as much. They have not released them. Instead, they made an offer to some local journalists to tour the consulate, in order to demonstrate that Mr. Khashoggi was not there. The staged tour does nothing to refute a grisly account offered by official Turkish sources — that Mr. Khashoggi’s body was dismembered and spirited out of the building. Again, if the government of Turkish President Recep Tayyip Erdogan has evidence of such a horrific crime, it should immediately make it available to the family and other interested parties.

For more than a year before his disappearance, Mr. Khashoggi was a resident of the United States, which gives the Trump administration a basis and an obligation to demand answers and relevant evidence from both Saudi Arabia and Turkey. So far, senior U.S. administration officials have had little to say publicly on the matter, which is concerning. If Mr. Khashoggi was murdered inside the consulate, it will cast the Saudi regime and its de facto ruler, Crown Prince Mohammed bin Salman, in a new and disturbing light and require a thorough reevaluation of U.S.-Saudi relations. Better to know that sooner rather than later.