"Whatever your plan is, it's going to fail. I'll make sure of that."
The year is 2183 A.D. Humans don't just planet hop — they board starships and teleport via Mass Relays to neighboring star systems and star clusters. Nanotechnology and cybernetics have advanced far enough to be able to bring a deceased person back to life. A physics phenomenon called "mass effect" has been discovered, and creatures naturally capable of sensing and manipulating it can enhance their prowess with the aid of brain implants. But despite all these leaps in science, turmoil still abounds among the stars. The Milky Way Galaxy is governed by a collective body of sentient races called the Council, among whose duties include hiring and dispatching military personnel of various skills and alliances to restore order where needed. One of these is a human named Shepard, the protagonist of the Mass Effect universe.
Commander Shepard's character is built on myriad customization options. While BioWare typically markets him as male, the player can choose to make her female, with the default first names being John and Jane respectively. His/her beginning class may be either a Soldier who's proficient in weapons, an Engineer with a solid grasp of tech items, or an Adept who manipulates the titular "mass effect" in battles. As the player gains experience, combinations of these classes become available. Shepard's birthplace and honed morality are also selectable. Was he/she born on Earth, in space, or on one of Earth's extrasolar colonies? Is he/she a glorious war hero, the lone survivor of a brutal battle, or a coldhearted murderer who cares only about the job and the paycheck? These choices affect everything from Shepard's in-game charisma to the tools he/she can handle to the supporting characters in the romantic subplot.
Shepard enrolled in a fleet called the Human Systems Alliance at the age of 18. Now 29, he/she explores the galaxy aboard a starship called the SSV Normandy, completing all manners of military assignments. Early in the first game, the Normandy crew investigates a human colony that comes under attack by a rogue Spectre, a member of the office of Special Tactics and Reconnaissance. In response, the Council appoints Shepard the first human Spectre, giving him/her the duty to hunt down the alien behind the assault, Saren Arterius. This task is neither simple nor the only one; the galaxy contains extensive side quests, dialogue, and story exposition to match its size and scope, and some of the player's choices affect not only how the game progresses, but also how the ending to one game will affect the beginning and development of the next. Talk about a mass effect.