Disclaimer: I am a noob so take everything I say with a grain of salt.
A sneaky mission although you don't have to do it that way. The aim is to sneak past all the guards with one merc and get to the mansion undetected. Well maybe other guys are better players than me but I found that impossible and so I just did it athletically. I filled my backpack with armour and medicine and snuck for the first few turns until I was detected and from then just ran flat out relying on my armor and their bad shooting to keep me alive. It would be good if you could sneak this mission but there seem to be a three choke points that I can't get past. I suceeded doing it this way fairly easily but the rewards are very poor, a little cash and reputation and only one merc getting the roughly 4-5,000 experience.
The alternative way to succeed in this mission is to take four angry and not at all sneaky guys in and kill all the pirates until in turn 20 you blow the smoke from your gun and walk calmly onto the target zone. I did it this way the first time.
As you are supposed to stealth the mission and fire no shots at all you get no in game rewards. I did this mission five times and never got anything at the end besides money and once an Air Force IOU. The one time I blasted everyone with four mercs I only found one ammo and some asprin. This is clearly not a farming mission!
Reach the mansion.
Take 1 mercs. For this mission you can take 4 mercs and slaughter everyone if you prefer.
Fire 0 shots. Even 1 to take out a wall would make this much easier.
20 turns. Easy if you stealth/run. Harder if you are fighting.