Cast

Eric O'Neill, a low-level surveillance expert with the FBI, believes he is accomplishing his dream of becoming a full-fledged agent, with his unexpected promotion and assignment to clerk for Robert Hanssen, a renowned senior agent with 25 years in the FBI. However, he soon learns the reason for his promotion is to gain Hanssen's trust and find proof that he is a traitor to the country. Determined to draw the suspected double-agent out of deep cover, O'Neill finds himself in a lethal game of spy vs. spy, where nothing is as it seems.
During World War II, spy Wu Lai-sheung is instructed by her superior Fan Yeung-shan to murder spy number 13 Cheung Chi-ping. While Wu establishes a relationship with Sakei, the assistant general of the Japanese army, she also gets acquainted with Cheung. Cheung and Wu fall in love. Wu recommends Cheung to become Sakei's driver. Cheung pretends to court the Japanese spy Siu-kuen, but Siu-kuen arranges to kill the spies contacting with him. Cheung has seen through Kuen's identity for long. When Kuen is going to kill Wu, Cheung kills Kuen, Fan compels Wu to kill Cheung. Wu follows the instruction to murder Cheung. After the murder, Wu disappears. After the war, Fan discovers Wu ends up in asylum. When he visits Wu, he tells her of Cheung's innocence. This breaks Wu's heart. Cheung turns out to have seen through Wu's identity for a long time and pretended to have been killed to cover up his identity and facilitate his work. With the truth known and the war ended, Cheung and Wu married.

Nicolai Dalchimski, a mad KGB agent steals a notebook full of names of "sleeping" undercover KGB agents sent to the U.S. in the 1950's. These agents got their assignments under hypnosis, so they can't remember their missions until they're told a line of a Robert Frost poem. Dalchimski flees to the U.S. and starts phoning these agents who perform sabotage acts against military targets.

North Korea's 8th Special Forces hijack a shipment of CTX, a potent new liquid explosive, and threatens South Korea as part of a plot to re-unify the two countries. Ryu and Lee, special agents of O.P., South Korea's secret intelligence service, attempt to track down the terrorists and find the CTX. Meanwhile Hee, the 8th's ultra-bad female sniper, resurfaces to wreak havoc and haunt Ryu.