You take the role of Joel, twenty years after the world went to hell due to the rapid spread of, basically, zombies.
Following me so far? Good. Anyway, in that time Joel has done a lot of things to survive. Some of which he's not proud of, whatever. Things have settled down somewhat these days, with Joel and his fellow survivors inhabiting a fortified city/town thing, the name of which I forget. Basically, you have military guarding the place tightly, with checkpoints and searches, and all those general high-security procedures that make life so much fun in the last surviving city on Earth.
This is kind of understandable, though-- whilst they're all about keeping their current citizens safe at all costs, a revolutionary group has sprung up claiming that there has to be a cure for the disease, somewhere.
These two sides pretty much have waged constant war for most of the past 20 years, as far as I can tell.
The world outside is massively overgrown by flora, and the occasional cloud of spores make travelling risky.
Anyway I could ramble on and stuff but I really don't want to spoil anything. I already feel a little sick just submitting this much.