Chisato Chisato lives with her only son, Akihiro, and chooses a man for remarriage who turns out to have an abnormal sexual appetite. Though he appears at first to be a kind and sincere husband, beneath that mask lies a twisted desire. Chisato is tormented by this man, gradually fueling his madness. Eventually, his desires extend to her son Akihiro. Their entwined bodies, writhing like insects deep underground, evolve into a masochistic relationship blending love and hatred. As maternal duty clashes with feminine instinct, Chisato's reason quietly and silently collapses.