From the Nintendo website:
You are Bren McGuire, on a United Planets Freedom Forces mission to save the peaceful planet Katakis from the Machine, source of all that is cruel and evil in the universe. The only weapon on your side is the state-of-the-art Turrican Assault Suit.
Equipped with multiple weapons, including the incredible Freeze-beam, that temporarily immobilizes almost any enemy, the Turrican Assault Suit gives one man the power of an entire army. Use the myriad weapons and powers at your disposal to fight through 12 increasingly insane levels, free the innocent residents of the planet Katakis, and crush the oppressive Machine.