The red rain fell.

Someone tweeted that they heard a big explosion, and all kinds of guesses and unclear information began to spread on the Internet.
What's more, people started to talk about a false rumor that if the red rain touched you, then you would turn into a vicious zombie and attack people.
This thriller story is about the people who escaped to a building where the internet connection and phone lines were down.
Some of them believed the information, some didn't, and some used it....Why did they gather together? What is the reason?

This movie is styled after "rewind", showing the scenes starting from the end.