Citadel: Garrus

Citadel: Garrus is obtained from Captain Anderson, shortly after your first meeting with the Citadel Council. You first need to speak with Harkin, down in Chora's Den in the Wards.

The next step is the Med Clinic, down in the Wards. You engage in a firefight but are able to save the attending physician, Dr. Chloe Michel. She tells of a quarian who offered information relating to the geth. She also mentions that she referred her to Fist, an agent for the Shadow Broker. Garrus also mentions Wrex, leaving you with a choice; locate Wrex first, or Fist.