A large derelict from the 1957 returns to Earth, crashing down on Washington D.C. in the year 2301. The city is evacuated beforehand. General Craig looks into its origins by researching old records. The craft is named the Nautilis, weighing 1,750,000 tons. The government sent it during the Venusian War I, seeking the mineral Z-71, rare on Earth but discovered plentiful on Mercury.