Can you help me with a story line for a 6 part zombie role playing game? (See details)

I want to run a d20 modern zombie campaign. (I don’t want to talk about gaming systems—we have the d20 modern books and I’m going to use them). I’d like it to be a mini campaign with a 6 episode story arc. The players, who are all experienced, would be playing ordinary people trying to survive in a post zombie apocalypse. I’ve played in campaigns that went on and on, one for more than 10 years, and others that really didn’t go anywhere. I want this story to have a beginning, a middle, and an end. The beginning would be discovering the zombie plague, and the end would either be a wipeout of civilization, or the party are heroes in saving civilization.

What I’m looking for are ideas for a story arc. I have my own research sources (zombie movies, podcasts, books, etc.) but I thought it might be fun to ask y’all for ideas.