If you've done some of the Hlaalu faction quests, you might already know that Drinar is a smuggler. At any rate, you'll need to enter Drinar's house and have a look around (his house can be found on the west side of Ald'ruhn, by the Ald Skar Inn). The door is unlocked, and Drinar is home. If you take a careful look around, you will find a single Dwemer Tube among the red pots on the large table near Drinar, who doesn't mind if you take it.
If you kill Drinar, Imsin is disappointed but impressed with your honesty in admitting it: you receive five Legion reputation points and her disposition still increases by five.
If you already have the Dwemer tube along with you when starting this quest, Imsin's dialogue is different.
The two locked chests on the main floor contain some raw ebony, but chances are that opening them and taking the ebony will provoke Drinar into attacking you.
There are also lines of dialogue describing Vorar Helas as the smuggler and scripts to update the quest when he is killed. Evidently at one stage he was the quest target instead of Drinar.