"He told me: I fled because I wanted my family to survive, but they all died. So, what was the point of me leaving home? If I had stayed, at least we would have died together," Liu says.
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He was most impressed by the fact many survivors had forgotten the disaster, while the youth hadn't even heard of it.
"People forget something only if it's unimportant or too commonplace," Liu says.
"Henan has suffered famines since the Eastern Zhou Dynasty (770-256 BC). They've always had people who starved to death, sold their wives and ate their compatriots.
"I found something peculiar about our people - when disasters happen frequently, they forget or dispel them with black humor."
Black humor colors the film.
A woman refugee volunteers to marry a young man, because the marriage would give him a wife, so he'd have something to sell. It is win-win: The man gets money, and the woman finds someone to feed her.
Such scenes have put audiences in stitches, which Liu takes as a compliment.
"I'm intrigued by the refugees' humor and convey that to audiences," he says.
"The great writer Lao She once said he wanted to write a tragedy filled of laughter. I think that's the real tragedy. When something really horrific happens, there must be something laughable in it."
"I take both their laughter and silence as signs of the film's impact," Liu says.
"The novella and the film are like needles that prick a numb body."
The script ends with an old survivor picking up a girl on his way home and taking her as his granddaughter.
Flowers suddenly blossom around them as they walk.
The scene does not appear in the film because the special effects don't match the film's grinding tone. But Liu believes in warmth and beauty deep in his heart.
"We present human nature's darkness in the novella and film, but darkness only becomes so when contrasted with brightness," he explains.
"Even in the darkest times, I believe in the kindness of ordinary people - even if it's small and fragile."
Contact the writer at liuw@chinadaily.com.cn.