Four strangers wearing restrictive bracelets on their wrists are seated in a spaceship about to depart from an Australian spaceport for a penal settlement on Mars. While guards attend to the final checks for the flight, which will be made on autopilot, the four exchange details of how they came to be prisoners. Their crimes range from the commonplace to the bizarre. One of them also has knowledge about the voyage which, out of an unexpected sense of compassion, he finds he is unwilling to share. As the ship lifts from the spaceport, this otherwise disparate group discover a common humanity that allows them to face the journey together.