The inhabitants of a multi-generational spaceship which has been in flight for 900 years, have no idea why they have been travelling for so long and what the original purpose of the journey was. They only know that some day, a tremor will be felt within the ship, signalling the end of their long space trip. Only one man knows that when the end comes, he is to read a long bequeathed set of instructions which will then reveal their true destiny.