Zhang Xiaojing is a former soldier in the Longyou Army who served on the frontiers of the Tang dynasty. After retiring, he joined the local security of the city of Chang'an, the heart of the empire, but he was imprisoned and sentenced to death after an incident in which Zhang killed 34 members of a gang that murdered his former Army commander Wen, and then killed his current commanding officer.
Zhang is unexpectedly reprieved when plans for a major rebellion are uncovered, involving a terrorist cell, the Wolf Squad, which has slipped into Chang'an before the Lantern Festival, one of the most spectacular days in the ancient Chinese calendar. To secure the safety of the Chang'an people, the Jing'an Si (Department of City Security) grants Zhang a special 24-hour amnesty, and he is ordered to catch the terrorists and foil the plot before the day is out. If he succeeds, he will be freed, otherwise, he will be executed. But to his surprise, Zhang discovers that he has been drawn into a far greater conspiracy against the empire than anyone had suspected.
Here's the trailer of the drama :
