This quest automatically begins after completing "Behind Enemy Lines". Your task? Answer a summons from Sloane Kelly. You and Sloane haven’t exactly gotten along well up to this point, so it’s doubly strange that she’d call on you. Return to Kadara Port and enter the Outcast Headquarters, where you’ll find Sloane waiting for you. Talk to her and she’ll tell you the news… bad news for her, but it looks like the Charlatan has finally provoked Sloane into seeking out a final confrontation. Due to the Charlatan’s infiltration of her forces, she can’t trust her own allies (which makes one question how she plans to cling to power) and so she’s turning to the Initiative Pathfinder for help. Desperate times…
Sloane Kelly was right about the future of Kadara depending on the outcome of this mission, so there’s no harm in going. Who knows, you may actually get an opportunity to shape the political future of Kadara? Make your way to the badlands and fast travel to the Sulfur Springs Forward Station. From there drive uphill to the south to reach a fork, at which point turn southwest until you reach another fork. At this second fork veer off to the west and follow the road as it veers north and leads into the mountains. You might want to save your game here, in case you want to see how things play out and make a different choice.
Drive uphill to the north until you find a cave, inside of which Sloane is waiting. Talk to her and agree to enter the cave with her, where she’ll confront the Charlatan - which just so happens to be a familiar face about Kadara. The Charlatan and Sloane will agree to duel, but your role is secondary and reactionary. Simply watch at the two square off (and circle around - there’s a lot of geometry involved in dueling!) When you get an interrupt prompt, press [R2]/[RB] to save Sloane from the Charlatan. You’ll get a second interrupt prompt as the Charlatan flees, but this one isn’t nearly as important, as it - and how you respond to Sloane afterwards - really just flavors the political relationship you’ll have afterwards without actually changing any details. On the other hand, if you choose not to intervene, the Charlatan will end up getting the best of Sloane.
Play kingmaker, after which you’ll have to discuss terms with whomever ends up in control of Kadara Port. With Sloane you’ll have to trek back to her headquarters in Kadara Port to finalize things, while the Charlatan will meet you back at Tartarus… after, perhaps, you settle out some personal details with the Charlatan, depending on some dialogue choices you’ve made along the way. Either way, you’ll earn 73 AVP, +5% Kadara viability and 1,330 XP. More importantly, the powers-that-be are now ready to accept an Initiative settlement on Kadara. You just need to activate the vault and deal with Kadara’s water problem.