Bounty hunter Samus Aran follows a distress call to the crippled Space Pirate vessel Orpheon, only to discover its crew decimated by their own biological weapons. After fighting her way through the ship and barely surviving its detonation, she tracks a mechanized version of the menacing Ridley to the planet Tallon IV below. There she uncovers the devastated civilization of the Chozo, an advanced species destroyed when a meteor impact unleashed Phazon, a mutagenic substance that has corrupted the world and drawn the Space Pirates' attention for its exploitable power. As Samus navigates Tallon IV's dangerous environments and contends with the Pirates' sinister agenda, she gradually unravels what befell the ancient Chozo and the escalating peril that Phazon represents to the entire region.