Metroid Fusion , the direct sequel to 1994's Super Metroid, sees Samus Aran sent back to planet SR388 to assist a Biologic Space Labs investigation team. While on the planet's surface, Samus is infected by a previously unknown parasite, known as X, which nearly kills her. However, she is saved by a vaccine made from the Metroid she had previously encountered on Zebes.
With the explosion that rocks the Biologic Space Labs, Samus must now investigate the damaged facility, which is orbiting SR388. The game follows a similar structure and gameplay to the classic side-scrolling Metroid games, featuring a large interconnected environment that Samus can explore as she learns new moves and weapons.