The story takes place aboard the Vessel, a spaceship that originally set out to guide humans, known as travelers, to a new planet. After the travelers died, the ship became inhabited and run entirely by robots. The travelers whose minds were preserved through a process called embedding are growing weak as the Heart, the presence that gives life to the ship's robotic inhabitants, decays and causes the machines to falter. Playing as the robot Mio, the player explores the Vessel in an effort to restore the Heart and carry out the ship's original mission.