Mars
Shepard still wasn't clear on why Hackett had sent her here. His message was barely audible. The parts she picked up on was something about a weapon located at the archives. If it could help them against the Reapers they might as well check it out.
Of all people Shepard expected to run into was Cerberus. Why were they here? Did they know about this weapon too? What was the Illusive Man planning? Seeing Cerberus again prompted Kaidan to question Shepard again. She did her best to explain she had no idea why they were here, but part of her knew he still didn't trust her just yet.
Surprisingly, Liara was at the archives as well, working here to uncover the weapon. If they could get the blueprints before Cerberus did, they might just have a way against the Reapers.