Yoo-bang (Lee Beom-soo) sneaks into a villa at night and discovers the dead body of Chunha Medical Group executive Ho-hae (Park Sang-myun). His niece Yeo-chi (Jung Ryeo-won) is hiding in the room. At the funeral, both Yoo-bang and Yeo-chi get arrested for murder. How did things come to this? It all began three months ago when Chunha began trial testing for their new medicine. In exchange for a job recommendation from Ho-hae, Yoo-bang agrees to join the trial testing and steal information about the drug. Rival company director Hang-woo (Jung Gyu-woon) is also there undercover to find out about the new drug. Spoiled rich girl Yeo-chi is undergoing training because her grandfather wants her to inherit Chunha one day, though she herself is completely uninterested. For the trial testing, 30 testers, including Yoo-bang and Hang-woo, are shut off from the outside world for 10 days. During the trial period, strange things begin to happen...
Hero of the series who is a bright and optimistic man. He steals the heart of Yeo-chi. His historical analogue is Liu Bang, the first emperor of Han dynasty.
A man who tries to get revenge against Chairman Jin for his father's suicide. His fiancée is Cha Woo Hee. His historical analogue is Xiang Yu, the self-styled "Hegemon King" of Western Chu.
A woman who is engaged to Hang-woo, and whom Yoo-bang is very close with. In an earlier draft of the script, Woo-hee dies after reuniting with Hang-woo, but the script was modified to give fans a happier ending.[4] Her historical analogue is Consort Yu.
Antagonist of the series. She worked as the secretary for Jin Si-hwang, whom she later kills to become the company chairman herself. She manipulates people to do her bidding, among them her colleague Park Bum-jung, who sincerely loved her. In the end she goes insane after she is found guilty for conspiring to kill Jin and the attempted murder of Woo-hee. Her historical analogue is Zhao Gao, an official who served all 3 emperors of the Qin dynasty yet played an instrumental role in the dynasty's downfall.[5]