If you recruited Garrus to your crew in the Mass Effect Legendary Edition, once you gained his trust, he shared a story with you about his work at C-Sec. There was a dishonest doctor at the station, Dr. Saleon, who used his patients as live test tubes, filled them with organs and later dissected them. Dr. Unfortunately, Saleon left the station before his arrest, but Garrus always kept an eye on him. He shares with you the coordinates of where he believes he is a doctor and his desire to follow him.
If you are going on this mission, you definitely want to take Garrus with you.
Where to find the ship Dr. Saleona
Dr. Saleona can be found in Kepler Verge. It should be right down where Virmire is, south of her, in the Herschel system. When you get into the system, the ship you are looking for is called MSV Fedele. Click on it to board the ship. It is said to be owned by Dr. Heart.
Finding Dr. Saleona
Dr. Saleon will be in the back of the ship. You must go through the primary area to get to it. The ship’s largest room will be full of test subjects who look like dry Husky, similar to what you fought with Geth and Feros. They will be the “test subjects” of the doctor and will be sour. When you arrive at the back of the ship, Garrus will want to make sure it’s properly positioned and can’t cause further damage to the rest of the galaxy.
When you get to Dr. To Saleon, Garrus will want to put him on the ground, but if you play Paragon Shepard, you can choose an alternative and have them arrested by the military. Garrus may disagree, but admits. Regardless, the doctor decides to run away and becomes hostile, forcing you to kill him. After graduating, Garrus will note what it was like, but you can give him a better answer for choosing an alternative.
At this point, you can always be in charge, whether Shepard or Garrus finish the doctor. Regardless of your choices here, Dr. Saleon won’t leave.
After completing the mission, leave the sector, complete another side mission, and return to Garrus to talk about how things happened. He will have a deeper commitment to the mission, regardless of your outcome.