After his own son brutally murders his wife and daughter, a Hong Kong man questions his own parental culpability in the horrific crime

This film starts with a horrific crime: without warning, a 15-year-old boy stabs his mother and sister to death with a kitchen knife in their Hong Kong apartment. Based on real events, this intelligent, understated drama asks the question that’s on everyone’s lips: why? It tells the story of the killings through the eyes of the boy’s father, a man of few words named Yuen, played with tremendous subtlety by Sean Lau in a performance that glimpses at the grief and guilt behind his character’s often expressionless face.

The film moves quickly back and forth in time. In the present, Yuen is coming to the end of a night shift at the family’s 24-hour restaurant when he spots police in the apartment block opposite where he lives. Yuen’s son Ming (Dylan So) has killed his mother Yin (Jo Koo) and 12-year-old sister (Lainey Hung). In the days afterwards, Yuen goes through the motions, picking coffins for his wife and daughter, organising the funeral. His mind drifts back to Ming as a boy, running into nursery on unsteady toddler feet, speeding on his first bike.