Please note that while this campaign uses the Serenity rules, it does not take place in the Serenity universe. It takes place in our own solar system, but in the future.
The year is 2293, and mankind has managed to spread out beyond our planet and colonize the rest of the solar system. Mars has been terraformed (nearly), and there are bases on moons and asteroids all over the system, as well as space stations that are privately, corporate, and government owned. Mankind has become a space race, and many people have not even set foot on Earth, instead have grown up in the vast reaches of space.
Science fiction has almost always made space feel fairly small. Where Star Trek will make an entire species inhabiting a whole sector of space feel like one small village, in this campaign, space is appropriately enormous. One solar system is all that this game takes up, our own solar system, but without faster than light travel, everything feels huge.
The world looks a lot like ours. An extremely wealthy upper class that controls almost everything but only is comprised of about 0.5% of the population. An almost non-existent middle class, and an enormous lower class that breaks their back for small wages just to try and keep food in their stomachs and a roof over their heads. The Government exists all over, but is mostly focused on the core worlds, which basically comprises the space between the sun and the asteroid belt. Even then, they're mostly focused on Earth, since that's where the majority of the population exists. The further out you get, the more lawless things become. There's no area of space where things are basically existing in an anarchistic state, but basically out past Jupiter, and especially beyond Pluto, you'll find that the laws and the rules of the Government just get a lot more blurry. Especially when the nearest law ship is days, sometimes even weeks away.
You are part of a crew aboard a freelancer cargo ship that does odd jobs out in the void. You've done everything from mining asteroids to hauling medical supplies. It's a hard life, and you've had to do things that aren't strictly legal (or even moral), but you've gotten by doing the best you can. But during a routine cargo drop-off that took you from Neptune to Earth, and the better part of three months spent without any contact with the outside world, you discover something unbelievable. The whole planet has been taken over by the Undead!
How will you survive? The entire solar system will be open to you, and it'll be up to you where to go and how to deal with the collapse of infrastructure. Do you stay on Earth, where the threat is the greatest but there is also the biggest source of renewable food and resources, or do you opt to take your crew out into the black, taking your chances on dwindling resources over the undead horde? The choice is yours....