Il dottor Sean McNamara e il collega Christian Troy sono amici di lunga data. Entrambi chirurghi, hanno filosofie di vita molto diverse tra loro: mentre uno è un dongiovanni sregolato, l'altro è il classico posato uomo di famiglia.

The lives of Bodie and Doyle, top agents for Britain's CI5 (Criminal Intelligence 5), and their controller, George Cowley.

The mandate of CI5 was to fight terrorism and similar high-profile crimes. Cowley, a hard ex-MI5 operative, hand-picked each of his men. Bodie is a cynical ex-SAS paratrooper and mercenary whose nature ran to controlled violence, while his partner, Doyle, comes to CI5 from the regular police force, and is more of an open minded liberal. Their relationship is often contentious, but they are the top men in their field, and the ones to whom Cowley always assigned to the toughest cases.

Yoo Seol-Ok liked mystery novels and wanted to become a detective, but she gave up her dream after marrying. Now, she is a housewife with a husband who works as a prosecutor. She meets Ha Wan-Seung. He is a passionate detective and they decide to collaborate to solve cases.