Mass Effect Story Explained: Plot Summary and Ending of the First Game

Mass Effect is the first game in BioWare's trilogy, released in 2007 and set in 2183. It introduces Commander Shepard, the Citadel and the Reapers, and sets up the war the next two games pay off. A lot of it depends on choices you make, and this page describes those as choices rather than one fixed version. It contains full spoilers for the whole game. (Mass Effect)

Before the story begins#

In 2183 humanity is a newcomer to galactic politics. The Systems Alliance found Prothean technology on Mars 35 years earlier, fought the turians in the First Contact War and opened an embassy on the Citadel, where the Citadel Council of asari, salarians and turians rules. Humanity wants a Council seat and a human Spectre, one of the Council's agents who work above the law. Shepard is an Alliance officer whose past is the player's choice: raised on Earth, on ships or on a colony, and known for surviving a massacre, for heroism during the Skyllian Blitz or for a ruthless victory. Where the series is going is on the Mass Effect timeline. (Mass Effect)

Eden Prime and the Citadel#

The game opens aboard the new frigate Normandy SR-1, commanded by Captain David Anderson with Shepard as executive officer. The turian Spectre Nihlus Kryik is aboard to assess Shepard as a Spectre candidate. The ship is sent to the colony of Eden Prime to collect a newly unearthed Prothean beacon, but when it arrives the colony is under attack by the geth, synthetic beings who hadn't left their own space in nearly 300 years. (Mass Effect)

On the ground Shepard finds Gunnery Chief Ashley Williams, the last of her unit, and a dock full of people turned into husks. Nihlus goes ahead and is shot in the back by a fellow Spectre, Saren Arterius, whom he trusted. Saren has used the beacon and leaves, and when Shepard reaches the beacon it pulls Shepard in and floods Shepard's mind with images of death and machines before exploding. (Mass Effect)

On the Citadel, the Council won't act against Saren without proof. Shepard works through the station's underside with C-Sec officer Garrus Vakarian and the krogan mercenary Urdnot Wrex, and finds the evidence through a young quarian, Tali'Zorah. She carries a recording from a geth's memory in which Saren and the asari Matriarch Benezia talk about the return of the Reapers and something called the Conduit. The Council strips Saren of his Spectre status and makes Shepard the first human Spectre. Anderson, who once lost a Spectre bid because of Saren, hands over the Normandy. (Mass Effect)

Feros, Noveria and the Reaper behind Saren#

Shepard can take the next three missions in any order. One lead points to Benezia's daughter, the archaeologist Liara T'Soni, who is trapped in Prothean ruins on Therum while geth try to capture her. Shepard rescues her, and she joins the crew. She has spent fifty years studying the Protheans and doesn't side with her mother. (Mass Effect)

On Feros, a colony built on Prothean ruins, the colonists are under the control of the Thorian, an ancient plant creature that Saren had come to bargain with. Shepard kills it and frees the asari Shiala, Benezia's former acolyte, whom Saren had handed over to the Thorian. She passes Shepard the Cipher, a Prothean way of thinking that makes the beacon's vision clearer, and whether she lives afterwards is the player's choice. (Mass Effect)

On the icy world of Noveria, Shepard confronts Benezia at a research lab where a corporation has been reviving the rachni, an insect race wiped out about two thousand years earlier. Benezia explains, in a moment of clarity before she dies, that Saren's flagship Sovereign has been controlling her mind. Shepard then meets the last rachni queen in a tank. Whether to let her go free or kill her is the player's choice, and it echoes in both later games. (Mass Effect)

Between missions, the batarian Balak tries to drop an asteroid onto the human colony of Terra Nova, and Shepard stops him in the Bring Down the Sky add-on. It's a side story and doesn't touch the main plot. (Mass Effect: Bring Down the Sky)

Virmire#

Salarian special forces under Captain Kirrahe have found Saren's base on Virmire. Saren has been using Prothean technology to breed krogan cured of the genophage, an army for his cause. Wrex wants the cure saved for his people and turns his gun on Shepard. Depending on what Shepard says and has done, Wrex either backs down or is shot, by Shepard or by Ashley. (Mass Effect)

Inside the base Shepard finds a second beacon, which fills in the vision, and talks with Sovereign itself through a hologram. It's not a ship at all. It is a Reaper, a vast machine intelligence, and it tells Shepard that the Reapers wipe out every advanced civilisation in the galaxy in a cycle and that organic life can't stop it. Saren believes that if he proves useful, organics can be spared. (Mass Effect)

To destroy the base the team plants a nuclear bomb, and Shepard has to choose between going back for Kaidan Alenko, guarding the bomb, or for Ashley, with the salarians. There's only time to save one. Whoever is left behind dies when the bomb goes off. Which one the player saves is a free choice, and the survivor appears in Mass Effect 2 and 3. (Mass Effect)

Ilos and the Battle of the Citadel#

Back on the Citadel, the Council grounds the Normandy to avoid a war in the Terminus Systems, and ambassador Donnel Udina goes along with it. Anderson breaks protocol to release the ship, and Shepard and the crew steal the Normandy and head through the Mu Relay to Ilos, the location the vision pointed to. (Mass Effect)

On Ilos a damaged Prothean VI, Vigil, tells the whole story. The Citadel and the mass relays were built by the Reapers to steer life down a path they could predict. Every cycle, when civilisations had settled on the Citadel, the Reapers came through it from dark space and took the galaxy apart system by system. Sovereign is the Reaper left behind to signal the station's Keepers to open the way. The last Protheans on Ilos sabotaged that signal and built the Conduit, a hidden relay to the Citadel, so Sovereign now needs Saren to open the station by hand. (Mass Effect)

Saren goes through the Conduit with a geth army. Shepard follows, landing on the Citadel just as the geth seize it and Sovereign attacks. Shepard reaches Saren at the Council chamber and can either persuade him that he was indoctrinated, in which case he shoots himself, or kill him in a fight. Sovereign then takes over his body. (Mass Effect)

The ending explained#

In the final minutes of the Battle of the Citadel, the Council's flagship Destiny Ascension is under fire, and Shepard chooses whether to send Alliance ships to save it or hold them back to focus on Sovereign. Saving the Council costs human lives. Letting it die leaves humanity as the most powerful species in Citadel space. Either way, Shepard's team destroys Saren's remains, which brings Sovereign's shields down, and the Alliance fleet and the Normandy destroy Sovereign. Shepard is found alive in the wreckage. (Mass Effect)

Afterwards, Shepard advises on the future of the Council. If it survived, humanity gets a seat on it. If it died, humanity leads a new Council. Shepard also recommends who becomes humanity's first councillor, Anderson or Udina. In the closing speech Shepard warns that the Reapers are still out there and promises to find a way to stop them. (Mass Effect)

What it means is simple: Sovereign was one Reaper, and the rest are waiting in dark space, but the Council would rather believe Sovereign was a geth ship. The questions left open are how the Reapers will try to come back without the Citadel, and who will listen to Shepard. Mass Effect 2 answers the first quickly. Weeks later, the Normandy is attacked by an unknown ship and Shepard is killed. (Mass Effect; Mass Effect 2)

What it sets up#

Every big choice here carries forward with a save import: the Virmire survivor, Wrex, the rachni queen, the Council and the human councillor. Mass Effect 2 picks up with the Collectors and Cerberus, covered on the Mass Effect 2 story page. For the whole series in one place, see Mass Effect story explained, and for the larger war, the Battle of the Citadel and Eden Prime War pages. (Mass Effect; Mass Effect 2)