In the film 'Alienoid', a swordsman in the Goryeo Dynasty seeks to seize a legendary divine sword, while others pursue an alien prisoner trapped in a human body in the year 2022. When a time door opens between the Late Goryeo Dynasty and the present day, chaos ensues as aliens appear on Earth.

Ean has a critical mission to return to the future to save everyone. However, she becomes trapped in the distant past while trying to prevent the escape of alien prisoners who are locked up in the bodies of humans. Meanwhile, Muruk, who helps Ean escape various predicaments, is unnerved when he begins sensing the presence of a strange being in his body. Traveling through the centuries, they are trying to prevent the explosion of the haava.