Drama series follows the life Jang Yeong Sil (Song Il Gook): a scientist, technician and inventor during the Joseon period. Jang Yeong Sil was born in the lower class nobi. King Sejong (Kim Sang Kyung) notices his abilities and brings him to the palace. King Sejong grants him a chance to display his abilities. He invents tools like astronomical instruments, iron printing press and a water clock.