400 Days has the player following five different characters as you see snippets of how they handle the early days of the Zombie Apocalypse. All five stories are around the same general area, a small roadside diner, though not all of them actually end up going to the diner. Instead, an observant gamer will notice props in the background that will show just how or where the current character ties into the rest of the stories.
What you end up getting by the end of the DLC is not only a glimpse at some of the tough decisions each character has to face, but also an overall view of the events surrounding this part of the country.