The relationship was nevertheless intense, not least because Mr. Khashoggi was going through a wrenching breakup with his home country. After a long career as a loyal supporter of the Saudi monarchy, he was becoming a dissident. He had moved to the United States 18 months earlier and begun to write columns for The Washington Post.

The main target of his criticism was the young and powerful Prince Mohammed, the de facto leader of Saudi Arabia, who was modernizing the country but also locking up opponents.

Many of Mr. Khashoggi’s friends had been imprisoned, and he felt obliged to raise his voice on their behalf, Ms. Cengiz said. “He was always talking about the moral responsibility he bore,” she told the Turkish news outlet Haberturk. “He was saying, ‘I have the opportunity, for my friends, for what they could not write.’”

In her book, Ms. Cengiz recounts an evening when he called in low spirits. He told her that Saudi prosecutors were seeking the death penalty against Sheikh Salman al-Awda, a reformist cleric. He said he despaired of making any difference with his writings. “Sometimes I don’t know what to do, and I am just stunned,” she recalled him saying. He began to weep.

She tried to encourage him. “This is a world of tests, and you have to do your best with the opportunities you have,” she told him. After the call ended, she also burst into tears. “He shared his sorrow,” she said. “It was a very hard day for me.”

In view of what was to come, however, “even these sorrows were happy moments in a sense,” she reflected. “Even sharing this kind of pain with someone like him is a good memory, a great happiness.”

Her father had reservations about her marriage to Mr. Khashoggi because of the age difference and concerns about his health, but allowed her to make her own decision. He asked Mr. Khashoggi to buy an apartment and settle it on her.