The military base's scientists have created a cyborg for combat. Los Santos is controlled by rebels, and it's up to him, and the 3 other soldiers to liberate it back.

Notes: In order to make your military buddies follow you, you have to give them a little shove first. I'm not sure why this happens but hey, the game wants to be a game. You might have to do a lot of babysitting with the soldiers due the game's horrendous AI. (or you could just leave them behind)