A spaceship travels into the unknown through distant space. Due to the theory of relativity the metabolism of the crew is very slow in their time only 30 years have passed, but a millennium has gone by in the Earth time. During their voyage the computer reveals a secret, the crew is only a metabolic time measuring device. The ship flies close to the speed of light, and due to the contraction effect the duration of the flight cannot be established in any other way but with the length of human life.