This Assignment can be accepted once you speak to Garrus enough times aboard the Normandy. It takes place on a ship that you must explore on foot.
How to Begin
While on-board the Normandy, you’ll find Garrus down in the cargo hold. When speaking with him, he’ll eventually open up about one of his old cases, Dr. Saleon, and how he got away. He’s managed to find the whereabouts of him now and asks if Shepard will assist him, beginning the Assignment.
Find Dr. Saleon
Once accepted, use the Galaxy Map and make your way to the Herschel system in Kepler Verge, there you’ll find the MSV Fedele. Once on-board, make your way into the main room and you’ll encounter Dr. Saleon’s Test Subjects. Like Thorian Creepers on Feros, these enemies will cause lethal damage if they melee you or have the ability to cause Toxic damage from range. With that in mind, keep your distance, use Biotics to disable them and make use of any Containment Cells scattered around in the large room.
Once the room is clear, make your way to the back and enter the room on the right to find Dr. Saleon himself. Despite your choices here, there’s no way to avoid a confrontation with him, thankfully he’ll put up little resistance. Once he’s dead, you’ll get some more dialogue with Garrus based on how you directed him before, ending the Assignment in the process. Be sure to take the time to loot Dr. Saleon’s room before leaving the ship, there’s plenty of worthwhile items on offer.