The series receives its subtitle from a theoretical mental complex attributed to the adaptation of cybernetics into the mass public. In the story, 'stand alone complex' is said to describe copies with no original and is portrayed by copycat crimes with no original criminal or, in other words, an imaginary criminal. It also refers to the structure of each first season episode: each episode can be viewed independently of each other, and there is little catch-up (if at all) given in each episode to keep the viewer up to date (unlike many anime series). The individual episodes are discreetly marked either "stand alone" or "complex" in the title screen. The "complex" episodes are more closely entwined with this encompassing plot, and the "stand alone" less so.
Taking place in a fictional city of Japan called New Port City in the year 2030, SAC tells the story of a special operations task-force called Public Security Section 9, or simply "Section 9". The series follows the exploits of Section 9's agents who range from ex-military to ex-police to even ex-mafia as they address each case and how it affects them on a personal level, eventually leading to the mysterious figure dubbed by the media as "The Laughing Man".
If you like nice action, deep stories, utterly BEAUTIFUL animation, and rich dialouge, watch it on Adult Swim. Or better yet, get the DVD releases- Amazon should have them.