This survivor pack replaces the L4D1 survivors with Basic HeavyTroopers From Halo REACH. But don't let the word "BASIC" fool you. These survivors have names and memories as well. They each have fought their own battles before and have overcome them with both their skills and their teamwork. How did they end up in this universe you ask? I will tell you. After receiving orders to perform a "strategic retreat" from the attacking alien species known as the Covenant, these men fought their way to an underground facility on the planet REACH. This facility was like no other that they have ever seen before. It  held many relics of a past civilization that was far more advance than that of us Humans. With no end in sight these survivors happened to come upon a working teleporter. While their planet was slowly being glassed, they had no choice but to enter the possibly dangerous teleporter. After a few seconds of debating to see who would go first, their peaceful talks quickly turned to violence. They all ended up going through at once, overloading the teleporter, they were sent to a different time in a different dimension. They now find themselves stranded on planet that could only have been Earth in the early 21st century. Though this Earth was not the Earth they once learned about in school. No, This Earth was inhabited with the undead. Now the question is, does the story continue? That answer my friend, lies in your skills against the undead.