Set in ancient China, Zeng Jing is a skilled assassin who finds herself in possession of a mystical Buddhist monk's remains. She begins a quest to return the remains to its rightful resting place, and thus places herself in mortal danger because a team of assassins is in a deadly pursuit to possess the remains which holds an ancient power-wielding secret.

It is the late 1920s when six-year-old Yingzi and her family move to Beijing. As Yingzi explores the busy streets and alleys, she befriends a widow who, driven mad by grief, stands vigil at the entrance of her hutong, waiting for her missing daughter to return.