When the Reapers were defeated at the battle of Earth, the galaxy believed that Shepard was killed with the activation of the Crucible super-weapon. However, known for embracing the impossible and overcoming these challenges.
Shepard found himself in the vast waste of a desert of an uncharted planet, fully healed and thoroughly equipped. Finding his way back to the Systems Alliance might prove difficult, but what would a good challenge be if it's easy to solve?