The plot will be presented in two parts; note that the characters may go through the first, second or both parts. It can be easily extended, in fact, I require your aid in making it sufficiently complete.
The plot is designed for the Firefly setting.
Part 1:
The characters are contacted by the farming family of Leatherbeats. They need to be at least somewhat trustworthy, previous experience or a recommendation through someone well-known is necessary. They would have to be really trusted for the whole truth. Most probably, they will only say their grandfather has been kidnapped.
The grandfather was suffering of a serious mental disease, so he could be fooled into doing something unwise (like, writing a third of the farm he still owns to the culprit).
The search begins, the information in the lists below is in order of how easy it is to get; the latter points on these lists will take more time, money or contacts or favours.
Some general information is available directly on the farm, suspicion will quickly fall on hands that have left. More can be learned in the town.
Succeeding in that, the kidnappers can be traced into the hills, where they want to repair a derelict ship to secretly leave the planet.
If things go well here for the kidnappers, the ship will be repaired in a few days and they will flee. The story might end here with the gunplay, but the characters may be offered a place in the crew, plus a cut of the treasure this grandpa supposedly knows of. Proceed to Part 2 then.
Part 2: (depends on whether the characters have a ship of their own)
It should be kept in mind the bad guys have served on ships before, Anatol being a pilot and Wilson having a little mechanical experience, navigation being his main job. If need be, they can easily take control of a ship. Their relationship is not exactly friendship, but they won't easily betray another for money, it had to be a real sum readily available. They may pretend to take sides, though. Note that they will try to keep the nature of the 'treasure' a secret for as long as possible, which puts them at an advantage in any negotiations or threats of death.
There are several possibilities to advance the plot:
Option 1: Transport - standalone, having a ship, the characters are hired to fly the kidnappers where they want to.
Option 2: Bad guys - the characters are recruited on the kidnapper's ship as crew.
Option 3: The Chase - with the kidnappers escaping, the PC's have to follow with their own ship.
Option 4: On their own - an option good characters should not take.
Lastly, you may be interested what the great plan of the kidnappers was.