In 1953, the Korean War ended in an armistice. A fragile peace has held since then, encouraging some to speak of - and work towards - reunification of the two Koreas. Then again, both sides have planned and executed a number of assassinations, espionage missions and military strikes in the intervening years.
In 1968, North Korean commandos attempted to assassinate South Korean president Park Chung-hee - the father of current South Korean president Park Geun-hye - at the Blue House (the South Korean head of state's executive office and official residence). The South Korean government responded by forming Unit 684, whose task was to assassinate North Korea's then leader Kim Il-Sung. In 1983, North Korean agents detonated a bomb in the Burmese capital of Rangoon, hoping to kill the visiting South Korean president Chun Doo-hwan.
South Korean spy thriller Shiri (1999) takes place against this historical backdrop. The film opens in 1992 with a montage of the incredibly brutal training of a group of North Korean commandos led by Park Mu-young (Choi Min-sik). The selection process is as simple as it is motivational: failure at any task means death.
The most skilled and lethal of these trainees is Hee (Kim Yun-jin), a female sniper who shares a cursory, but significant emotional involvement with Park. Her training ends when she is sent to South Korea as a sleeper agent.
In 1999, a group of these same commandos arrive in Seoul on a mission. They hijack a shipment of CTX, a new and extremely powerful explosive. With Hee's aid, they set in motion a plan that will have catastrophic effects if it succeeds.
Two South Korean agents, Ryu (Han Suk-kyu) and Lee (Song Kang-ho), have been obsessively searching for Hee after she assassinated a number of South Korean officials. After the CTX is stolen, Ryu and Lee are tasked with finding it and stopping both the commandos and Hee. In addition to tremendous work pressure, Ryu is also having a difficult time with his fiancée, a recovering alcoholic who owns the tropical fish shop where they met.