The drama is based on a manhwa with the same title. Tamna the Island is set in 17th-century Joseon times as a young English castaway, William, comes to the island and meets the characters played by Seo Woo, Im Joo-hwan, and Lee Sun-ho. The name “Tamna” refers to what is now called Jeju.
The drama is about the assassination attempts on Emperor Jeong Jo's life during the 8 day period when he left the palace for a ceremony to honor his father who was killed by his grandfather.