In a retrofuturistic cyberpunk Equestria, Rainbow Dash and a special team of astronauts are sent to Mars to investigate potential future off-world colonization. But when they prepare to head home, they find that a terrifying alien lifeform has stowed away on their starship. Trust between them dissipates as each of the crew members are assimilated one-by-one by perfect imitations that must be uncovered and destroyed before they reach Earth.