An alien scourge threatens to destroy Earth's solar system, but with so many Legionnaires expelled, injured or missing, the remaining heroes stand virtually no chance of stopping the threat...until the United Planets forces them to recruit five of the most powerful beings in the cosmos: the Fatal Five!

To fight an approaching Sun Eater, the Legion learns of a group of meta beings the United Planets had engineered for such a contingency. The Legionnaires must now assemble this difficult group - the Fatal Five.