There's a doorway on Mars that has mankind's greatest minds perplexed.Deep beneath Aeolis Mons an ancient secret is revealed, and a team of explorers led by Forest Judge, Deputy Commander of Gale Base Alpha, are dispatched to investigate. The prehistoric gateway reveals a biosphere preserving Earth's distant past, and as Judge and crew stand on the threshold of mankind's greatest discovery the Martian ground trembles.A roar thunders from within, the doorway closes, and the team is trapped.Six mission specialists, each with unique skills, each with different reasons for wanting to break free of the primordial trap. To get home Judge is forced to choose between escape and changing the course of humanity.What will he do?