Human overpopulation depletes Earth's resources, leading humanity to build an interstellar ark. It carries 60,000 people on a 123-year trip to colonize Tanis, an Earth analog. The passengers are placed in sleeper ship, and a rotating crew wake biennially to maintain the ship. Eight years into the mission, the ship receives a transmission from Earth in multiple languages: "You're all that's left of us. Good luck, God bless, and godspeed."