Nine powerful families referred to as the "Old Nine Gates" or the "Mystic Nine Clan" guard the town of Changsha during the era of the republic.
Zhang Qishan (William Chan) who is the leader of the nine gates, investigates a mysterious train that ends up at his Changsha station that leads to a mysterious mine.
In order to solve the mystery, he entrusts in the help of Qi Tiezui (Ying Haoming)and Er Yuehong (Lay Zhang) who is an opera singer from a family of archaeologists.
Before they can start their mission, they must find medicine to help Er Yuehong's wife who is terminally ill.
Along the way, they'll meet the young mistress of the hotel Yin Xinyue (Zhao Liying) and discover a dangerous plot that could take down the people of Changsha.
Will they be able to help Er Yuehong's wife and unravel a mystery that could save their people?
"The Mystic Nine" is a 2016 prequel to "The Lost Tomb."