In a rundown boarding house in Hong Kong, the residents become convinced they’re witnessing the presence of a vengeful spirit when an enigmatic girl shows up, asserting she is the twin sister of a tenant who has mysteriously disappeared. Consumed by guilt, the tenants start dying one after another. As a detective delves into what seems to be a series of suicides, he uncovers a chilling truth: the karma people dispense returns to them with double the force.