Being able to see ghosts and other supernatural spirits is a heavy responsibility. Prince Lee Rin (Jung Il Woo), like his father before him, discovers that he has the ability to see ghosts and other supernatural beings. Armed with his newfound abilities, Lee Rin becomes the leader of a group of night watchmen who patrol the streets from dusk to dawn to protect the people of the Chosun Dynasty against evil spirits. Moo Seok (Jung Yun Ho) is the best swordsman in the land who is the prince’s trusty bodyguard. But their loyalties will be tested when they both fall in love with the same woman – Do Ha (Go Sung Hee), the successor of the Ma Go tribe who seeks their help to protect the Baek Do mountain’s spirits. But Park Soo Ryun (Seo Ye Ji), the daughter of a court officer, will stop at nothing to marry Prince Lee Rin. “The Night Watchman,” also known as "Diary of a Night Watchman,".