How to Find the Master Thief in "Mass Effect 2"by Seth AmeryUpdated September 22, 2017
Before Shepard ships off to the final end run mission concluding "Mass Effect 2," one additional ally appears in the universe waiting to be recruited for the job. A truly enigmatic thief whom few have ever have the privilege of seeing, Kasumi Goto can be found -- when she's ready -- hiding in the heart of the Citadel.
Complete the mission "Freedom's Progress." If you're starting out with a brand new save file, you're in luck; this is the first true mission of the game, although you must deal with the initial cutscenes and tutorial before approaching this point. Either way, when the mission is complete, you'll receive a message from the Illusive Man about Kasumi's dossier.
Plot a course to the Citadel. As soon as you dock and exit the Normandy, you'll see the marked advertisement terminal straight ahead of your path. Interact with it to begin a conversation with the cleverly hidden Kasumi.
Reveal the secret password, "Silence is Golden," to gain her trust and have her agree to join your ranks. Despite the Illusive Man's insistence on this password, you can easily use "Cut the Crap" to recruit the thief anyway.
Return to the Normandy to find Kasumi on the observation deck waiting to give you her loyalty mission, "Stealing Memory." Although you're not required to complete this challenging mission before the end of the game, it's in hers and Shepard's best interests if you do. It's probably in yours, too; if you don't complete her loyalty mission, then you won't unlock her Flashbang Grenade or Shepherd's formal attire to wear on board the ship. Besides, if you paid extra for the added content, why not enjoy it?
You must have "Kasumi - Stolen Memory DLC" in order to receive this dossier and obtain the thief as part of your crew.
Talking to Kasumi in her room on the Normandy can elicit some interesting glimpses into her past, especially if you examine some of her possessions. She also offers some insightful observations about the rest of the crew from time to time.
Even though her master thievery has brought her this far, she's just as susceptible as the rest of Shepard's crew to the dangers of the final mission. Like any other character, if you don't complete her loyalty mission, don't count on her surviving to the very end.