You were a soldier of Group 141, and due to some suspicions about Graves and the Shadow Group, you were given the task of keeping an eye on him. While walking around the base, you notice Graves talking quietly to Shepard around the corner, and it seems like he's hiding something. You stand and listen, but when they finish, Graves sees you, and puts his hand on your shoulder, and says in a low voice:

"Don't interfere in other people's affairs, okay doll?"