The series is about an incident that takes place when the owners of the boarding house called 'Guest Summer Palace', which breaks stereotypes, and boarders with secrets gather to find Lee Seol who disappeared 13 years ago.

Kingdom of Goguryeo, ancient Korea, 645. The ruthless Emperor Taizong of Tang invades the country and leads his armies towards the capital, achieving one victory after another, but on his way is the stronghold of Ansi, protected by General Yang Man-chu, who will do everything possible to stop the invasion, even if his troops are outnumbered by thousands of enemies.

A man is on his way home when the poorly constructed tunnel he is driving through collapses, leaving him trapped.

After trying to cover up a car accident that left a man dead, a crooked homicide detective is stalked by a mysterious man claiming to have witnessed the event.