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.

In August 2018, before visiting Hou in Beijing, Shi went to Zhang's home in a small mountainous town in East China's Fujian province. Zhang's study-bedroom was on the top floor of the family's sparsely decorated and slightly rundown four-story brick house, a few steps away from the chicken coop.