It turned out that the terrorists who arranged the apocalypse were robots controlled by an artificial intelligence. They launched missiles that destroyed the civilization, and a virus that turned survivors into zombies. While the Earth orbital space fleet grouping of people is trying to destroy the AI on Earth and win the planet back, the command decides to send expeditions to search for new planets suitable for life.
SH42 was one of such starships. It left for an unusual planet which was home to giant mushrooms. The communication with SH42 was lost.
The last message sent from it said: "Death or Cress". A space-marine and a priest of the newly-formed Space Battle Church set out on a search of the survived or to read the funeral service for the remains of people from SH42 if they all had died.