In Stay Alive, random events happen. If you're lucky, the event will be minor, like a zombie making it into the house where the survivors are hiding. It could be a lot worse than just one of the hungry dead.
The rules include character generation for 24 different Strains (versions of humanity that survived through the apocalypse), faith powers and psionics as well as advice on running stories, weaving webs of intrigue and more procedural investigations.