Coming after the events of Metroid 2: Return of Samus, the intergalactic bounty hunter Samus Aran has discovered a Metroid larva, which after hatching immediately identified Samus as its mother. Samus then takes the baby to to the Ceres Space Colony where scientists believe they can harness the Metroid's power. The last Metroid is in captivity. The galaxy is at piece......... Until Ridley the dragon takes the Metroid for the villain, Mother Brain. Samus must track the Metroid down, fight Ridley, various aliens creatures and space pirates, and of course the deadly mother brain.