The story is about a group of humans wage war against the rising evil of unidentified parasitic life forms that live off human hosts and strive to grow their power.These parasites fall from the sky and then begin to attach themselves to human hosts, turning them into deadly machines. They literally take over the entire person, feeding off of them and then controlling their minds. These parasites can change their shape, When these creatures invade their hosts, they turn them into scary things with very sharp parts sticking out. A group of humans, led by a military police force called The Grey, fights against these parasites to protect humanity.
A detective (Kwon Hae-hyo), a burnt-out young man (Koo Kyo-hwan), and a young woman (Jeon So-nee), who all have personal connections that drive them to fight against the invasion. They fight against the parasites and they also encounter mutants.
While the special effects are impressive, showcasing the grotesque horror of the parasite attacks, some character actions and story progressions feel inconsistent. The leader of The Grey, initially portrayed as strong and decisive, becomes uncertain in later episodes, and the motivations of the parasites are basic and predictable.
Even though it has some problems, the show mixes scary stuff, science fiction, and feelings very well.The show stays fun with cool fights and spooky parts. religious ideas makes more interesting this series and helps us think about how different people can live together.