"Unit 404" is a sci-fi puzzle platformer game. The story takes place in the year 2182, in the near future. The world has been destroyed and mankind has been forced to live in underground shelters. You are one of the few who have managed to survive and build an artificial civilization. The government is still trying to find a way to protect the world from the threat of the alien invasion.

To do that, a new type of experiment is being conducted in an abandoned building. The building has been left empty and is now occupied by a strange entity. As soon as the first residents of the building started to disappear, the government decided to send you and your friends to check out the situation. You are to find out what kind of entity is living in the building and how to deal with it.

It is up to you to find a way out of the building and return to the world.