Samus Aran, the last Metroid, has discovered the plot of the villainous Raven Beak, who plans to take over the galaxy with the power of Metroid that lives within Samus. Even she can deny her appetite no longer… even the Ultimate Warrior must feast.

Samus Aran has conquered the “X” parasite, proving herself as the Ultimate Warrior. Some time after she destroyed the Metroid breeding program by a rogue cell of the Galactic Federation, the mainline Galactic Federation (which had no culpability in the breeding program) received a mysterious video transmission showing a living “X” parasite on the planet ZDR. After the Federation lost contact with their E.M.M.I. robots on the surface of ZDR, they have hired Samus Aran, the last Metroid, to investigate.