Down by the landing pads in Paradise, you'll find Nexus human Kent Halsey.
He'll ask you to help track down his sister, Isabel- a troublemaker who got exiled from the Nexus and kicked off Kadara. Agree, and he'll send you to talk to a turian inside the trading post.
Ask her nicely, and she'll give up a navpoint for Isabel, but hints she may be in trouble. You'll find Isabel's cave to the northwest, in the Languish area. Outside is a fairly large enemy encampment.
They're mostly vanilla Raiders, but there's a lot of them, with good cover- Don't let yourself get outflanked. Also keep an eye out for a Pariah playing the spoiler.
At some point, Isabel will call you inside. Despite what she says, make sure you've killed every raider out here before entering the cave. If any are left alive, the next stage of the quest may not trigger.
When the slaughter is complete, enter the cave to confront Isabel.
This is one of those rare conversations you can 'lose.' If you want Isabel to reunite with her brother, chose the options "You need to leave," and "What about family?" She'll relent and pack her bags. The quest terminates without reward (likely a bug), but you can follow up with Kent back at the port for some epilogue.
In another technical oddity, you may find datapads referring to a plot against Isabel elsewhere on the planet, even if she's already left. Likewise, the guards outside her cave continually respawn (which can be handy if all you're looking for is a fight).