Gurus in the late Goryeo dynasty try to obtain a fabled, holy sword, and humans in 2022 hunt down an alien prisoner that is locked in a human's body. The two parties cross paths when a time-traveling portal opens up.

The ‘Beast Cop’ Ma Seok-do heads to a foreign country to extradite a suspect, but soon after his arrival, he discovers additional murder cases and hears about a vicious killer who has been committing crimes against tourists for several years.