One month after the events of Metal Slug 3, the threatening presence of General Morden looms over the world once again. Marco Rossi and Tarma Roving of the Peregrine Falcon unit reunites with Eri Kasamoto and Fio Germi of SPARROWS as the quartet is ordered to investigate Morden's latest plan, being joined by two new allies named Ralf Jones and Clark Still of the Ikari Warriors. Together, they proceed into the mountains where Morden's Rebel Army has established an outpost. (wiki)