Give President Trump credit for bringing unjustly detained Americans home. Whatever misgivings you may have about his North Korean diplomacy, three American prisoners freed in May are better for it. So is Pastor Andrew Brunson, whom Turkey released this month. “I hope my husband is next,” Hua Qu tells me. “He has literally been taken hostage by Iran.”

Her husband is Xiyue Wang, a history graduate student at Princeton arrested in Tehran in August 2016 and sentenced to 10 years in the notorious Evin Prison. He is one of at least five Americans currently detained in Iran—and the only one who doesn’t also hold Iranian citizenship.

Mr. Wang, then 35, ventured to Iran in January 2016 to research the Qajar dynasty, which ruled Persia from 1794 to 1925. The espionage allegation came after he copied thousands of pages of research material from the National Archives of Iran. As one of his Princeton professors put it, Mr. Wang was accused of “spying on the dead.” The documents he copied were from between 1840 and 1910, according to Ms. Qu.

She received a phone call from her husband Aug. 7, 2016. He told her he had been interrogated at a Tehran hotel for several hours, but things looked OK. He was back at his apartment, and there was someone downstairs who would escort him to his flight back to the U.S. But Mr. Wang never got to the airport, and his wife didn’t hear from him for 20 days.

Then “he suddenly gives me a call,” Ms. Qu says. “He told me he was arrested and they put him into solitary confinement.” Mr. Wang’s captors had repeatedly interrogated him and threatened to hold him forever unless he confessed. Mr. Wang acquiesced and was moved to Evin’s Ward 209, a wing for political prisoners. He remains in Evin today.