In the future, humanity becomes more technologically-advanced. People manage to create a technology of supersonic flights, which allows them to reach distant areas of the space. As such, people meet the other civilizations. You will play for Shepard, the special agent who serves interstellar Citadel. Together with people and aliens, you will fly even further and discover new areas of the galaxy. When following the betrayer of your team, you suddenly stumble at the real threat for the entire universe – ancient civilization of intelligent machines.