In the 21st century, humanity tried to colonize Mars by dispatching two species capable of surviving the planet's harsh conditions to terraform it: algae and cockroaches. However, they failed to foresee the species' extraordinary adaptive capabilities. By the 26th century, a deadly illness called the Alien Engine Virus has reached Earth, and the cure is believed to exist solely on Mars. The complication is that contemporary Mars is dominated by beings dubbed "Terraformars," highly potent and intelligent humanoid cockroaches that evolved from the original organisms sent to the planet. The Annex I squad, made up of one hundred men and women genetically modified with traits from powerful Earth organisms, has been deployed to Mars to identify the origin of the Alien Engine Virus and assist in curing humanity—marking the beginning of the crew's struggle for survival.