The film tells the story of an 11-year-old girl, Dada, who suffers from psychological distress and troubles due to a sudden change in her family situation, leading to emotional depression and withdrawal, ultimately forcing her to drop out of school. Her mother has no choice but to send her to live temporarily at a horse ranch run by her cousin.

兩起懸案，二十餘年，追兇歲月裏的各自淬煉，終以責任與執念共同告破。

大唐敦煌，重镇漠州。安史之乱后，漠州陷于河西匪军之手，大唐守军全数殉国。此后六十载，丝路断绝，生灵涂炭。匪军首领任光热凶残暴虐，倒行逆施，妄图“还民为奴”。
“狮子吼，唐军归。”这句流传了六十年的传说，是漠州人最后的念想。可铜狮沉默，唐旗无踪，传说能否应验？
名门望族张佑承隐忍多年，终于举事，归义火种在绝望中点燃。然而敌众我寡，漠州命悬一线，最后的希望落在仓皇出城的小队身上——狼鹞子、诺次、张月牙、曹光宗。
黄沙之下，埋着六十年前的唐军；壁画深处，藏着无人知晓的秘密。孤勇的旗手、神秘的张都尉、苦守石窟的廖黑云……那些被风沙掩埋的名字将逐一登场，一同回答那个问题：唐旗，还能不能重新飘扬在漠州城头？