In the midst of a prolonged conflict between the ISA and Helghast on the planet Vekta, ISA mercenary Ross and his comrade Huey encounter Chajans, the lone survivor of an ISA unit decimated by the Helghast forces. Moved by Chajans' plight following the annihilation of his platoon, Ross resolves to fulfill the fallen soldiers' mission of safeguarding a crucial target, driven by the promise of a valuable reward.