Nam Sang Mi plays widowed police officer Lee Sun Ae who finds herself suddenly immersed into international espionage by Han Yoo Il, an undercover agent. Lee Joo Hyun plays Kang Jun, who's recently transferred to the Criminal Investigation Department. He opens an old case involving Sun Ae's past that leads him to an entanglement between the current political/economic powers and their secrets. One of them, oddly enough, being Han Yoo Il. Who is this man? Why is he here?