I was thinking of shamlessly stealing the rough plot of Assault on Precinct 13 (or the original: Rio Bravo), where a facility is besiged by a gang of roughians. In this instance, the scenario would be a brothel on an old west planet. Why Brothel? One of my character's mother is a lady of ill repute (actually, I might promote her to Madam) and this is the first time the party is going to go meet her family.
The nearest town is a mining town run by a powerful family - an old childhood rival of the character from long ago who likes to lord over his subjects. Big fish small pond syndrome.
So, to sum up -
Character
Character's Madam mom
Character's childhood rival who runs the Company.
The 98 dollar question, the one I've been stuck on. Why would Big Fish cause trouble for the Brothel? What's a good hook for cause him to come do violence to the Madam and her charges? In Rio Bravo (and Precinct 13), the protagonists were guarding a prisoner that the antagonists wanted back. There's not really a MacGuffin like that in a brothel.
So, I'm willing to entertain ideas. What would you guys suggest for a MacGuffin?