Poseidon

A worldwide criminal syndicate called known as Heugsahoe exists. Their boss is Choi Hee-Gon.

In 2008, the leader of the Intelligence Investigation Team of the Maritime Police, Kwon Jung-Ryool (Lee Sung-Jae), forms a secret investigation team to capture crime boss Choi Hee-Gon. Soon, Jung-Ryool gets closer and closer to capturing Choi Hee-Gon. Then, Jung-Ryool's wife Min-Jung suddenly goes missing. Her dead body is then thrown in front of Jung-Ryool. Soon after, other family members involved in the undercover operation are killed.

Seon-Woo (Choi Si-Won) goes undercover on Jung-Ryool's order. Seon-Woo can't stop the mission, even though there's continuous threats on his life. Soon, a policewoman who investigates Seon-Woo is killed. It's clear the the woman's murder was committed by crime boss Choi Hee-Gon, but evidence is still lacking for his arrest. Finally, the undercover operation is abandoned.

2011 - 3 years later, Jung-Ryool appears obsessed with his job ... trying to forget the guilt he feels over the death of his wife. With the help of Hyun Hae-Jung (Jin Hee-Kyung) and a director of the maritime police, Jung-Ryool forms another special investigation team. To avoid the attention of others inside the maritime police and crime boss Choi Hee-Gon, the special investigation team is disguised as the #9 investigation team which is responsible for unsolved cases.

Seon-Woo has been demoted to the country maritime police office in Gunsan City. There, Seon-Woo busts an illegal trafficking organization and runs off with their smuggled goods. Seon-Woo now becomes a fugitive. This is part of Jung-Ryool and Seon-Woo's master plan to catch Choi Hee-Gon. They hope to go through middle man Jung Deok-Soo, nicknamed Popeye. Seon-Woo approaches Popeye with his stolen goods, but Popeye finds out the truth. Seon-Woo's life is now in danger. He is saved with the help tactical team leader Kang Eun-Chul (U-Know Yunho). Seon-Woo and Kang Eun-Chul were former colleagues.

Seon-Woo now joins the #9 investigation team. Seon-Woo also takes an interest in Corporal Soo-Yoon (Lee Si-Young). Meanwhile, Popeye kidnaps Kang Eun-Chul. The abduction of Kang Eun-Chul brings back memories of the slain police officer several years earlier.