Lady Vengeance (2006)

Imprisoned for thirteen years for allegedly kidnapping and murdering a six-year-old boy, Lee Geum-ja wastes no time in winning over her cellmates' sympathies. From the former prostitute who strangled her pimp to the old North Korean spy who hands her the "Sutra of revenge"-- illustrated instructions for crafting a handmade gun disguised as a prayer book--all the prisoners become instrumental in the scheme Geum-ja has meticulously drafted for her future as a free woman. Deprived of her baby daughter and of her youth, Geum-ja at first seems to accept her tragic destiny. However, she never strays from her plans to take a mighty revenge on the former teacher who betrayed her and slaughtered her innocence.