Mass Effect 2 begins as cinematically as the last one ended. The Normandy is attacked by an unknown vessel. Escape pods jettison, but Joker won’t leave the cockpit even as the ship burns and tears apart. We know from talking to him in ME1 that he suffers from bone brittle disease. It’s up to Shepard, walking through a hull open to space, to find him and carry him to the last pod. Normandy explodes, though. Shepard manages to eject Joker safely before she’s blown free, life support failing.
And then Shepard is in a medical bay. Someone has brought her back from near death and rebuilt her. It is Cerberus.
We meet the Illusive Man, the leader of Cerberus and the one responsible for ordering Shepard’s rescue. His second, Miranda, oversaw the two years of reconstruction necessary to save us. (Both of these characters are voiced by stellar actors who look like themselves thanks to a great animation team. It’s a really fun start to the game.)
Meanwhile, human colonies have been disappearing. Slavers are blamed by the government, which is too busy with diplomacy among the nations to look into this oddity. Only Cerberus pursues answers, and only Cerberus remembers the Reapers and wants to counteract whatever they have planned next. This is the arc of ME2.
The first mission is to investigate a newly hit colony before the site is contaminated by other investigators. The place is deserted except for a team of Quarians led by Tali. It’s awkward. Everyone hates Cerberus, and Shepard, who’s been dead for two years as far as the galaxy is concerned, is suddenly alive. One of the Quarians was here on Pilgrimage during whatever happened to the colony. He’s hiding and we must find him.
He has a data record. A rarely-seen race, the Collectors, attacked. They stung every human with some kind of neurotoxin, then packed them up and took the stunned bodies away. Now we have a villain, and a possible link back to the Reapers. Let the investigation begin.