"Back in 2017, while the family was living in Champaign, Yingying's father took the same daily walks," said Wang, father of an adult son and daughter. "He would walk and walk until, in the far distance, a corner of the student building where Yingying once stayed appeared in sight. There he would stop and stand, sometimes for hours on end, as if waiting."

On July 18 last year after the jury failed to reach agreement over a death sentence, Judge James Shadid sentenced 30-year-old Christensen to life imprisonment without the possibility of parole. Walking out of the courtroom, Hou told the waiting media in English: "For me, the result today seems to tell me that I can kill anyone with all kinds of cruel methods and I will not need to die for it. Me, myself, will never agree with that."

Not long before the trial, it was revealed to the Zhangs that in March 2017 Christensen went to UIUC's counseling center seeking treatment for his substance abuse issues and "suicidal and homicidal" thoughts.

In the wake of that revelation, the Zhang family filed a lawsuit against the university's counselors. It was dismissed on the last day of 2019, on the grounds that the counselors had not created or increased a "specific danger" to Zhang. The suit was filed again in state court and dismissed again in June.

Wang was scathing of the university, believed to have the largest number of overseas Chinese students among all US universities.

"There are nearly 6,000 overseas Chinese students at the university at this point. Multiply that number by four, and then by the annual tuition fee the university charges them; the result is phenomenal. The Chinese student community in Champaign was shaken by Yingying's tragic death, a time for the university to show that it really cares. But on certain occasions it opted for the opposite."

Wang says the university put the family in its graduate dormitory when they arrived in the US in mid-June 2017. Yet in August they were abruptly told to leave because the university said it had leased the apartment to some graduate students."We told the university authority that since the trial would not take place in the near future, the family was probably leaving the US in a few months, and that they were more than willing to pay. But no matter how hard we pleaded, the answer was a categorical no. So the family had no choice but to move out.

"By the time the family left the US in November that year, no one had moved into that apartment."

The lawyer, who keeps in regular contact with the family these days, says that throughout there has been "one and only one wish" for the father and that's to "bring Yingying home", a wish reiterated by the man when he left the US for the second－and quite possibly the last－time in late July last year, after the trial ended.

"Information concerning the disposal of Yingying's remains was put forward as part of a plea bargain proposed by the defense in late 2018. In such cases a defendant agrees to plead guilty or make a revelation in exchange for an agreement by the prosecutor to drop one or more charges."

"Our attitude at the time was: we would not object to a deal to remove the death penalty only if Yingying's body could be discovered as a result of Christensen's disclosure. But we were told by Christensen's lawyers that 'even if he tells you everything he knows, you may or may not be able to recover anything'.

"The Zhang family's position was part of the government decision not to go along with the plea bargaining. All things discussed in this process are considered hypothetical. In other words, although I don't think Christensen had a strong incentive to lie, none of what he said about the disposal of Yingying's remains should be taken as fact."

During the trial Hou exchanged emails with Christensen's father.

"I asked if we could meet Christensen in person after the trial," Hou says."I had always harbored hope that he might be driven by whatever remains of his humanity to tell us the truth. Christensen's father didn't give any definitive answer. But when I tried to contact him again after the trial he didn't reply."

In August, on Shi's behalf, two fellow alumni from Peking University visited the Zhang family in Fujian province, bringing with them a computer on which they showed the parents Shi's documentary. Throughout one of them held the mother tightly.

For Sun, the movie represents an effort to "look beyond the stereotype". "In American mainstream media we overseas Chinese students often appear as a group, a number, whose individual members are seldom given the attention they deserve. This is especially true in a central state like Illinois, where high unemployment has antagonized some against immigrants and foreign students."

Minutes before Zhang got into Christensen's car, she failed to catch a bus. A camera on that bus shows her running behind it...