One of the Zhang family's two lawyers, Wang Zhidong, partner of the Chicago law firm Wang, Leonard & Condon, was at the airport to meet Zhang's father, maternal aunt and Hou when they flew in on June 17, eight days after Zhang went missing. (For health reasons Zhang's mother was able to come to the US only in August, accompanied by her son, Zhang's younger brother.)

For the next two years Wang was with the family every step of the way as they negotiated the country's daunting legal labyrinth, heavy-hearted. "One of my main jobs was to try to make them understand the vast differences between the US and Chinese criminal justice system," he said."Given that the whereabouts of Yingying's body still remain unknown, it would have been extremely hard to convict Christensen if it was not for the secret recordings of their dialogues made by Bullis, who also turned up to testify in court when Christensen went on trial in June last year."

On June 30, 2017, the morning after the concert, Christensen was arrested. That afternoon the police summoned the family to their office, where they were told that Zhang was believed to be dead.

"No hope was left after that day," Hou says.

But some kind of hope had to be maintained, if only to prevent the bereaved from drowning in despair. This was what Shi and Sun felt when they met the Zhang family for the first time in the university dormitory where they stayed.

The news had clearly taken its toll-the father, Zhang Ronggao, looked haggard and was for the most part silent. On the other hand, Ye Liqin, the maternal aunt, was still speaking of the possibility of "Yingying being alive". "If she's dead, she would have appeared in my dreams," she said.

In the ensuing months Shi and Sun followed the family as they searched for Zhang, inadvertently retracing her physical and emotional journey in the foreign land.

In the movie the father stood in a windswept cornfield beside the towering equipment his daughter had set up with Miao, her fellow researcher, to monitor crop growth. The slanting sunlight adds a statuesque quality to the man's solitary, middle-sized figure, reminding Shi of his own father.