SPOILER ALERT: the following article contains massive spoilers, including the ending. If you have not yet seen the movie, proceed at your own risk, or better, come back to this article later!
SPOILERS AHEAD
Alienoid / Oegye+In 1Bu Summary and Synopsis
The door of time opens between the swordsman who wants to seize the legendary divine sword at the end of the Goryeo Dynasty and those who chase after an alien prisoner imprisoned in a human body in 2022.
Source: Wikipedia (CC BY-SA 3.0).