Wu Biao, with XYY Syndrome, is on a train with caregiver Old Liu. He faces provocations from Zhu Qiang and his wife: stealing seats, being loud, kicking his chair. Wu Biao, sensitive to noise and relying on medication for violent impulses, has his medicine bottle knocked over by Zhu Qiang. Pushed, he fights thugs hired by Zhu Qiang. Thanks to his mental illness diagnosis and self-defense, he avoids legal repercussions. His potential for violence remains a ticking time bomb.
