A nuclear energy program intended to unify the Korean Peninsula and make South Korea a global leader in the energy race becomes the target of a powerful and secretive global organization known as Athena. To protect the technology, a new counter-terrorism agency called the National Anti-Terror Service (NTS) is established. The story follows Lee Jung-woo, a highly skilled but bored NTS agent, whose life becomes anything but ordinary when he encounters the ruthless Son Hyeok, the director of an American intelligence agency who is secretly also a high-ranking agent of Athena. Son Hyeok orchestrates a series of plots to steal the nuclear technology, using Yoon Hye-in, a beautiful and enigmatic double agent who infiltrates the NTS and works undercover for Athena. Hye-in develops genuine feelings for Jung-woo, creating a conflict of loyalty. As the two agencies play a deadly game of cat and mouse across international locations including Italy, Japan, and New Zealand, Jung-woo gradually uncovers Hye-in’s true allegiance. After Hye-in defects from Athena to help Jung-woo, Son Hyeok is stripped of his rank and goes rogue, launching a personal vendetta against the NTS. The conflict culminates in a violent raid on the NTS headquarters, where Jung-woo and Hye-in face Son Hyeok in a final showdown. Hye-in shoots Son Hyeok to save Jung-woo, and Son Hyeok dies while sparing her life. Hye-in is granted amnesty and leaves South Korea, and a year later Jung-woo leaves the NTS to reunite with her in New Zealand, ending on a hopeful note.