Yoo Si-jin (Song Joong-ki) is the captain of a South Korean Special Forces unit. He catches a motorcycle thief Kim Gi Beom (Kim Min Seok) with Sergeant Major Seo Dae-young (Jin Goo). The thief is injured during his capture and is sent to the hospital. Dae-young realizes his cellphone was stolen by the thief and goes to the hospital along with Si-jin to retrieve his cellphone.
In the emergency room, Si-jin meets Dr. Kang Mo-yeon (Song Hye-kyo) for the first time. He falls in love with her immediately. Mo-yeon mistakenly assumes Si-jin is part of thief's criminal gang due to his nickname "Big Boss", which is actually his callsign. He proves to her that he is a soldier with the help of army doctor Yoon Myeong-joo (Kim Ji-won).
Si-jin and Mo-yeon begin to date, but due to their jobs, their dates don't go well. Si-jin takes an order to lead his soldiers on a peacekeeping mission to the fictional country of Uruk. Meanwhile, Mo-yeon is upset because she failed to become a professor due to a colleague's privileged background. When Si-jin and Mo-yeon meet again, they talk about their views on life and realise how different they are. Si-jin, as a soldier, kills to protect lives and Mo-yeon, as a doctor, tries to save lives. They say their goodbyes. Dae-young on the other hand faces a dilemma on whether to continue with his relationship with Myeung-joo or risk being removed from the army by Myeung-joo's father, Lieutenant General Yoon.
Eight months later, Mo-yeon rebuffs the sexual advances of hospital chairman Han Suk-won (Tae In-ho) and as a result is assigned to lead a medical team to Uruk. There, Si-jin and Mo-yeon meet and fall in love again. Through their encounters in Uruk—an earthquake and an epidemic—their love for each other grows stronger. While in Uruk, Mo-yeon accidentally confesses her feelings and the two officially start dating, much to the amusement of their respective teams.
Back in Korea, the two of them continue their dates until Si-jin and Dae-young are sent on an operation in which they disappear and are assumed to be dead. Months pass, and Mo-yeon mourns his death, deciding to commemorate his passing with a volunteer trip to Albania. This is where Si-jin eventually finds her after he and Dae-young are rescued from captivity by "a friend from afar", a soldier from North Korea whom Si-jin had earlier helped save the life of. Si-jin and Mo-yeon are happily reunited. Meanwhile Dae-young goes back in an emotional reunion to Myeung-joo, who is stationed in Uruk. In the credits, the entire team is once again called into action following a volcanic eruption in Canada.
- Song Joong-ki as Captain Yoo Si-jin (aka Big Boss)
- Si-jin is the leader of the five-member Alpha Team, including himself and Dae-young. He is portrayed as easy-going, playful, straightforward, and charismatic but also brave, skillful, and immensely loyal to his country. He often flatters and teases Mo-yeon with his romantic lines, especially about her beauty and "being sexy" in operating room. In the final episode, Si-jin is promoted to Major.
- Song Hye-kyo as Doctor Kang Mo-yeon (aka Beauty)
- At first, as a talented surgeon, Mo-yeon believes that her career will improve through hard work in operating room. Still, she became a victim of discrimination, with her application for a promotion being repeatedly rebuffed in favour of her colleague who comes from a privileged background. Plus, she had to substitute that arrogant colleague in a TV show. In the end, she was sent to lead a humanitarian mission in Uruk, as a 'punishment' for rejecting Director Han's 'love', where she finally meet Si-jin once again.
- Kim Ji-won as First Lieutenant Yoon Myeong-joo
- Myeong-joo is an army doctor and the daughter of a general. She has feelings for Dae-young, but her father disapproves due him being of a lower rank than her. Formerly, Myeong-joo was an intern at Hae-sung, and she attracted the attention of a man whom Mo-yeon had a crush on, causing a strain in their friendship. However, in the end, their relationship with their respective boyfriends bring the two close together.
- Jin Goo as Sergeant Major Seo Dae-young (aka Wolf)
- Known as Si-jin's closest friend, previously Dae-young was Si-jin's trainer. He and Si-jin often spend time together either in a mission or in a break. In terms of romance, Dae-young is soft-hearted and awkward. He gets the attention of First Lieutenant Yoon Myeong-joo who is Lieutenant General Yoon's daughter.
Alpha Team Members
- Park Hoon as Sergeant Choi Woo-geun (aka Snoopy)
- Choi Woong as Staff Sergeant Gong Cheol-ho (aka Harry Potter)
- Ahn Bo-hyun as Sergeant Im Gwang-nam (aka Piccolo)
Haesung Hospital Medical Services Team
- Onew as Lee Chi-hoon (1st year resident of Thoracic Surgery)
- Lee Seung-joon as Song Sang-hyun (General Surgeon)
- Seo Jeong-yeon as Ha Ja-ae (ER Nursing Team)
- Park Hwan-hee as Choi Min-ji (ER Nurse)
People at Haesung Hospital
- Hyun Jyu-ni as Pyo Ji-soo (Pathology Specialist)
- Tae In-ho as Han Suk-won (Chairman of Haesung Hospital)
- Park Ah-in as Kim Eun-ji (Thoracic Surgery Specialist)
- Jo Woo-ri as Jang Hee-eun (1st Year Resident of Anesthesiology)
Tae Baek Army
- Kang Shin-il as Lieutenant General Yoon (aka Yellow Tiger) (Myeong-joo's father)
- Kim Byeong-cheol as Lieutenant Colonel Park Byeong-su
- Kim Min-seok as Lance Corporal Kim Gi-beom (Platoon Sergeant as seen in EP 16). A pickpocket later enlisted to the army.
- Jasper Cho as Daniel Spencer (Peacemaker Emergency Doctor Team)
- Jeon Soo-jin as Ri Ye-hwa (Peacemaker Emergency Nurse Team)
- David Lee McInnis as David Argus (Gang Boss, former Delta Force Captain)
- Dean Dawson as the Chief of Police (Tae Baek Police Chief)
- Jo Jae-yoon as Jin Young-soo
- Lee Yi-kyung as Kang Min-jae
- Zyon Barreto as Fatima
- David Pipes as Martin (World Times reporter, episode 7)
- Ji Seung-hyun as Senior Lieutenant Ahn Jung-joon
- Kwak In-joon as Lee Han-soo (Minister of Foreign Affairs)
- Joey Albright as US Army Delta Force member
- Lee Kwang-soo as shooting arcade operator (episode 1)
- Lee Jong-hyuk as Captain Kim Jin-seok (episode 2, 5, 10, 15)
- Matthew Douma as Jordan, US Army Delta Force Captain (episode 2, 10, 12)
- Jung Ji-won as TV announcer (episode 2)
- Park Tae-won as TV announcer (episode 2)
- Ryu Hwa-young as Seo Dae-young's ex-girlfriend (episode 4)
- Jun In-taek as Yoo Young-geun (Yoo Shi Jin's father) (episode 6, 7, 15)
- Park Joon-geum as Lee Chi-hoon's mother (episode 7, 11)
- Yoo Ah-in as bank reception Eom Hong-shik (episode 13)
- Nam Ki-ae as Kang Mo-yeon's mother (episode 13)
- Red Velvet as themselves (episode 16)
Drama ni dah lama jua ditayangkan, tapi biasalah orang-orang yang tak mengikuti perkembangan ni bukannya tahu sangat, lagi-lagi citer korea, memang taklah. (saya la tu).
Asalnya, saya ternampak iklan DOTS ni kat TV. Sekali imbas, tengok macam hero n heroin dalam citer TK2H. Rupanya bukan... Tapi memang iras sikit-sikit apa yang mata saya tengok.
Saya dah ulang tayang citer ni beberapa kali dah. memang best giler lah. Lepas drama TK2H, citer ni paling win! Hihihi..
Sesiapa yang tak suka atau belum tengok lagi citer ni, saya sarankan sangat-sangat supaya anda tengok. memang takkan menyesal! Nasiblah kau 16 episod je... kalau tak habis migrain nengoknya.