Pegasus Bookstore is going through hard times due to competition from internet bookstores. Kitamura Aki and Nishioka Riko are employees at Pegasus Bookstore. Aki is 23 years old. She has a strong will and freewheeling personality. She places her job and dreams above marriage. Riko is a 40-year-old single woman. She is the vice-manager at the bookstore. She has pride in her work. The two women have completely different personalities.

25年前，年仅10岁的女孩葛城佐智绘被杀害，直到15年后时效成立，真凶都一直没有被抓获。当年亲眼目睹了葛城尸体惨况的医师乡田亮二（江口洋介 饰）辞去职务加入警队，2008年作为国际刑警回到日本继续调查此事。而在巴黎邂逅的女子（广末凉子 饰）竟惊人地宣称自己便是葛城佐智绘！
原来她是葛城太太痛失爱女后收养的孤儿，这些年来一直背负着佐智绘的记忆生活。随着乡田的深入调查，尘封已久的往事再次浮现出来，而佐智绘当年的同学亦纷纷出来追寻真相，当年小女孩的死都给年幼的同学们留下了难以磨灭的伤害。然而一个又一个被怀疑的对象出现，到底谁才是真正的凶手？25年前的迷案，最终能否大白于天下？