Female Convict Scorpion: Jailhouse 41

Nami Matsushima (Meiko Kaji) is locked up and bound in underground solitary confinement. She makes a weapon out of a spoon by holding it in her mouth and grinding it against the concrete floor. The chief warden, Goda, believes that Matsushima may inspire the other prisoners to revolt. The convicts escape to an abandoned village, where Oba reveals her crime: when she found her husband cheating on her, she drowned her 2-year-old son and killed her unborn baby.