Public Security Section 9 is an elite special ops unit that works directly under the control of the Prime Minister. They've been called in to rescue a high-ranking government official from a hostage situation. But something doesn't seem right to Major Motoko Kusanagi. After some investigating, Section 9 uncovers a major espionage plot, and it's up to them to prevent a major international incident.
The entire city of Nagasaki is evacuated and the JSDF moves in after a live nuclear bomb is found planted in the city, presumably by Dejima militants. Section 9 arrives to defuse the bomb and determine its precise origins.
The Prime Minister is taken into custody, and the military begins its strike on Dejima. The Major and part of Section 9 head to Dejima to try to hand over the nuclear device to the military there, in order to defuse the situation, while Ishikawa heads to SPring-8 to deliver the rest of the plutonium.
Kuze manages to take down the jamming plane, but becomes trapped in rubble with the Major. The Tachikomas begin discussing what to do about the nuclear submarine they have spotted, and Batou manages to convince the special forces that have been sent to kill them to listen to him.