One summer evening a couple years ago, Hua Qu’s son’s preschool teacher pulled her aside. Shaofan, Qu’s son, had been pretending that bad guys had locked his dad in a dungeon inside of a big castle that was guarded by scary dragon.

Was Shaofan just playing around?

Qu had tried to be discreet. But for months, she had been working nonstop to bring home her husband, Xiyue Wang, a Ph.D. student at Princeton who had been arrested and imprisoned in Iran. Now Shaofan had finally pieced together — in his 3-year-old mind — why his dad had disappeared.

Shaofan had been close with his father. Before Wang disappeared, he would walk Shaofan to daycare in the morning and pick him up in the afternoon. As a student, he had a flexible schedule. This allowed Hua to commute from New Jersey to New York, where she worked at a corporate law firm.

Then, in May 2016, Wang traveled to Iran to do archival research for his Ph.D. The trip seemed low-risk: He was studying ancient documents that had nothing to do with modern-day politics. Although the Iranian government had imprisoned several Iranian-Americans in recent years, Wang, a Chinese-born naturalized U.S. citizen who had already visited Iran once, had little reason to expect to be targeted by Iranian authorities.

But when he went to Tehran the second time, Iranian authorities blocked him from accessing some of the documents he needed. Then they interrogated, arrested and imprisoned him. Qu couldn’t get in touch with Wang for 20 days. He finally called her in late August, sobbing inside of Tehran’s Evin prison.

After Wang disappeared, Shaofan asked about his father constantly. He pointed to airplanes he spotted in the sky and asked if his dad was aboard on his way home. Qu told him she hoped his dad would come home soon. She didn’t know when Wang would return and didn’t think her son was old enough to hear the entire truth. But she didn’t want to lie.

Hua Qu Xiyue Wang with his son Shaofan before he was imprisoned in Iran.

Soon, lobbying on behalf of her husband consumed Qu’s life. She quit her job as a lawyer in New York and started working at a pharmaceutical company in New Jersey so she could be closer to home.

At first, Qu kept Wang’s imprisonment a secret, hoping for a quiet resolution to his case. She quietly pressed the Chinese government to intervene on Wang’s behalf. But the Iranians wanted a deal with the U.S. government, which had recently dropped charges against seven Iranians in exchange for the release of four Americans imprisoned in Iran. By the time Wang was arrested, President Barack Obama was in his final months in office and his administration didn’t have much leverage. Iranian officials have picked up at least four more Americans, including Wang, since the prisoner swap.

Wang languished in prison. In the beginning, he told Qu he thought about killing himself.

Two years passed. Shaofan stopped talking about his dad so often. Qu felt torn. She didn’t want Shaofan to forget about Wang. But she also didn’t want him to be miserable thinking about his dad all the time. She could tell Shaofan was suffering from Wang’s absence, even though he didn’t talk about it as much as he used to. He struggled in kindergarten. He seemed less confident playing outside with the other kids — his dad never had the chance to teach him to toss a ball around, and Qu doesn’t know much about sports. He asked her philosophical questions about the afterlife. Qu wondered if he was asking because he was worried about his dad.

After Wang disappeared, Shaofan asked about his father constantly. He pointed to airplanes he spotted in the sky and asked if his dad was aboard on his way home.

Last summer, after holding Wang secretly for almost a year, Iran went public with his case and announced his 10-year sentence for espionage. Qu switched her strategy, too. That November, she went on television and called on President Donald Trump to speak with Iranian officials about freeing her husband. Earlier this year, she spoke at a rally at Princeton alongside the town’s mayor. In September, she traveled to New York during the United Nations General Assembly to meet with U.S. officials.

These days, Qu speaks to the State Department once every week or two. State Department officials respond to her requests for updates but don’t usually have any new information to offer. She hopes that Trump, who has touted his administration’s efforts to free Americans from prisons in North Korea, Egypt, Venezuela, and Turkey will bring Wang home next. But the already-tense U.S.-Iran relationship has only worsened since Trump took office and withdrew from the 2015 Iran nuclear agreement — which had created the diplomatic groundwork for the last prisoner exchange.

In the meantime, Qu has to settle for near daily phone calls from Wang. She tries not to cry or let her husband know how stressed she is taking care of everything on her own. There’s nothing he can do, and he has his own problems: arthritis, a rash on his head and depression. Even in prison, he’s worried about finishing his Ph.D. He’s now years behind the other students in his cohort and doesn’t know how he’ll be able to complete his research even if he gets out.

He worries his son will forget about him.

In September, Qu had a rare piece of good news to share with her husband. When she opened Shaofan’s school folder, she found a picture he drew of himself with his mom and dad on either side and snowflakes overhead. Qu thinks Shaofan was inspired by memories of the last day the three of them had spent together. It was a cold day in January 2016, and the family had made snow angels and rode sleds down the hills of Princeton’s campus. It was the first time Shaofan included Wang in one of his drawings.

Hua Qu Shaofan's drawing of him and his parents.

But Shaofan rarely comes to the phone when Wang calls. Now five, he has lived about half of his life without his dad around. It’s hard for him to relate to the voice on the phone. Earlier this month, Wang asked Shaofan if he remembered riding on his shoulders during the walk to the local bakery to buy a donut or a bagel.

“I’m five, and you cannot carry me anymore,” Shaofan responded.

There was a long silence on the other end of the line.