Captain William D. Stanaforth (Mark Strong) is on a one-way solo mission, taking humanity's first steps toward colonizing Mars. Although the entire world is watching him, he is completely alone in a dark and distant sea of stars. Stanaforth rockets bravely through space facing insurmountable odds, but as the journey takes a toll on his life-sustaining systems, he is forced to make impossible choices that threaten his sanity, mission and very existence.