Synopsis
After his mother was brutally murdered in front of him by the Thai Qing Faction's gangster Mao, Lee Soo-hyun (Lee Joon-gi) was adopted into NIS agent Kang Jung-ho’s family. Together with Min-ki (Jung Kyung-ho), Jung-ho’s son, Soo-hyun becomes an NIS agent. Soo-hyun met Ji-woo (Nam Sang-mi) when they were about twelve years old and has another fateful encounter with her 10 years later. Together they have promises for the future.
One day, Soo-hyun leaves for an operation dealing with the Cheongbang, only to return in failure because of the resurfacing terrible childhood memories of when he was in Thailand. Due to his thirst for personal revenge, and ignoring orders Soo-hyun was fired and stripped of his title as an NIS agent. The head of NIS, Jung, proposes to the distraught Soo-hyun to infiltrate the Cheongbang. Through Chief Jung’s proposition, Soo-hyun becomes an undercover NIS agent after staging his own death (car accident). Hiding his past, Soo-hyun infiltrates the Cheongbang with revenge in mind, leaving Ji-woo behind. Under the pseudonym Kay, he passes through the backstreets of Bangkok. He plans on becoming one of Mao’s underlings to uncover Mao’s illegal business. What Soo-hyun didn't know was Ji-woo is the daughter of the same villain, who killed his mother and father.
Meanwhile Min-ki has fallen in love with Ji-woo and she begins to consider his proposal to officially court and forget Soo-hyun. Soo-hyun, now known as Kay, heard that Mao likes Muay Thai (Thailand Kickboxing), so Kay becomes a Muay Thai athlete, hoping Mao would see him. Mao came to one Muay Thai game in which Kay deliberately loses the match. At the fighter's resting room, he overheard conversation between a Cheongbang's Mini Boss and his subordinate planning to kill Mao. When Mao went up to the stage to honour the champion, the assassin aims at him but Kay saves Mao. Mao then took Kay as his right-hand man. Mao and his gang go to Korea to expand their drug business. They started a company called BS Enterprise. Kay's mission was to protect Ji-woo from the Korean gang, Spider.
The Spider Boss tries to kidnap Ji-woo, but little did they know Soo-hyun was protecting her by following around in his car under Mao’s orders. When Ji-woo was rescued by him, she was in great shock. He hides her from the Spider Gang by dropping her off behind the containers and backs right out of the dead end to engage in a dangerous car chase. Soo-hyun gets shot in the head and loses control, his car then falls off the port wharf into the sea. He wakes up later in a wise old lady's house. But he suffered from amnesia. Later, he gets kidnapped by the spider gang and is used as bait for their trap to capture Mao. Things get turned around and Kay kills the Spider Boss and saves Mao once again. Mao now sees Kay as not only his life savior but a son. For the Qing Faction gang, Kay’s words are Mao’s orders.
One day, Mao comes to Ji-woo (his daughter) and she sees Soo-hyun. She is in shock again. Later, she meets him again but does not believe it is him because of his jerkish attitude. He told her that she was heartless for rejecting her biological father when he went to see her and very selfish. She gets angry and when she gets home, she ripped up a picture she drew of him before.
While protecting Mao's girlfriend as she was shopping, Soo-Hyun's adopted dad sees him. He looked at him without recognizing him as his adopted father was checking him out. His adopted dad then tells the Chief of the NIS that Soo-hyun has amensia. They plan to save him from the gang. While on this mission, the Spider gang's follower (now part of Mao's gang) stabs Soo-hyun's adopted dad when he was trying to tell Soo-hyun that he is not Kay but Soo-hyun. This is where Soo-hyun begins to doubt himself as Kay.
The ex-follower of the Spider gang ran away after trying to persuade Kay to go with him. Min-ki arrives at the scene and sees Soo-hyun looking over his fatally wounded father. When his father dies subsequently at the hospital, Min-ki vows to kill Kay with his own hands.
Over the span of the next episodes, Min-ki and an old ex-NIS agent and restaurant owner form an investigation team secretly with two other NIS employees. Min-ki becomes obsessed with bringing down Kay and Cheongbang (Mao's gang). Ji-woo is convinced that Kay is Soo-hyun.
Read more about this topic: Time Between Dog And Wolf