When sent to investigate a Cerberus research base that's mysteriously gone silent, Shepard arrives to find Geth overrunning the base. The sole survivor, Chief Scientist Archer, paints a dire picture: an experiment to fuse a human volunteer with a virtual intelligence created a dangerous hybrid "VI overlord". The rampaging VI has already attacked three other Cerberus bases, controlling any technology it finds in an attempt to break freeâ€“and unleashing Geth across the planet. Unless Shepard can infiltrate the VI's fortress and shut it down, this homicidal intelligence will beam itself-off planet and wreak havoc on other systems. The action unfolds over five new level areas, with two new achievements.