Sometime after you first enter Solitude and Roggvir's execution scene plays, Jaree-Ra will appear on the streets across from Bits and Pieces. If you talk to him, he offers to help you earn some easy gold, while hinting at Deeja and his and thieving activities. If you walk away without listening to his offer, he will then go back to his job at the Solitude Docks and can be safely ignored. You can still hear his offer as long as both he and Deeja are alive. (If either of them die, the quest cannot start; however, the Icerunner will return.) If you decide to listen, Jaree explains his scheme to put out the Lighthouse fire so that the Icerunner will run aground and can be looted. You can then end the conversation either by accepting his offer or threatening to report him to the guards.

At this point, you have the option to go and talk to Captain Aldis. You can say that Jaree-Ra is up to something, but he does not tell you anything helpful, telling you to find proof. (That is, unless you happen to already have Hargar's Journal in your inventory, in which case it is possible to have Jaree-Ra arrested straight away and the Icerunner will return sometime afterward.)

From here, you can either choose to go along with putting out the Lighthouse fire (similar to vanilla) or search for evidence of Jaree's criminal activity. There are no immediate clues of where to look for this, but if you go talk to Ahtar the headsman, he has a job for you to track down a bandit leader that he accidentally let escape. This quest should point you to Broken Oar Grotto (note that this uses the radiant quest system so it is possible that another mod will cause this to randomly point to a different location). Broken Oar Grotto is the hideout of the Blackblood Marauders, led by Captain Hargar. Jaree-Ra and Deeja are allied with the Blackbloods, a fact which you will uncover after completing this dungeon. After defeating Captain Hargar, you can find Hargar's Journal, which reveals Jaree-Ra and Deeja's ties to the Blackblood Marauders and the fact that Jaree planned to use you as a scapegoat for his scheme. If you just want a quest marker to the journal, open the console and type in set STIHandHoldingEnabled to 1.

After recovering Hargar's Journal, you get two new options: Either report it to Captain Aldis or confront Jaree-Ra with it. Bringing it to Captain Aldis will cause him to put Jaree-Ra under arrest, after which he will reside in the Castle Dour Dungeon. Bringing it to Jaree-Ra allows you to force him to give up, and he'll go back to his normal job. Alternatively, you can attempt to persuade Jaree-Ra to go forward with his plan with you as a partner. This is an Average level persuasion check, although if Deeja has died, it will always fail. Once you've passed this persuasion check, you can use the Ebony Blade on either Jaree-Ra or Deeja to power it up. Note that killing Jaree-Ra at this point fails the quest (which still allows the Icerunner to return).

If you didn't end the quest another way, you can go ahead with the plan to put out the Lighthouse fire like in vanilla. Then you can go on to the Solitude Docks and meet Jaree-Ra, like in vanilla. If Deeja is dead at this point, Jaree-Ra will get angry and attempt to kill you. You can also go ahead and kill him here even if you were following the vanilla quest route.

After the Docks, go on to the wreck of the Icerunner. If you had killed either Jaree-Ra or Deeja at this point, the Blackblood Marauders will be immediately hostile to you. If Deeja is dead, the quest ends here, as she would not have been able to send the ship's loot to Broken Oar Grotto. Or if you have been working together with them, you simply talk to Deeja to complete the quest. Here you can also choose to betray Deeja and kill her if you like. If you're following either the vanilla quest route or the variant where you killed Jaree-Ra at the docks, the loot will have been moved to Broken Oar Grotto. Once you kill Deeja, you will find a note on her corpse saying as much. If you then go to Broken Oar Grotto, the quest completes once Jaree-Ra is dead. The treasure inside the "Icerunner Chest" at the end will be equivalent to what would have been on the ship, and much more substantial than what would be there in vanilla.

If you were working together with the siblings but turned on Deeja and killed her, then if you encounter Jaree-Ra afterwards, he will get angry and attempt to kill you.