Yoo Si-jin, a captain in the South Korean Army's special forces, and his friend Master Sergeant Seo Dae-young apprehend a thief, Kim Gi-bum, using toy guns. At the hospital, Si-jin meets Dr. Kang Mo-yeon and is instantly attracted to her, though she initially mistakes him for a criminal. Despite their growing relationship, Si-jin's frequent military duties and Mo-yeon's career frustrations strain their bond. Si-jin is deployed to the war-torn country of Uruk, while Mo-yeon, after being passed over for a promotion, is sent to Uruk as part of a medical team. In Uruk, Si-jin and Mo-yeon reunite and deepen their understanding of each other's professions while facing challenges like an earthquake, a deadly virus outbreak, and a corrupt warlord. Mo-yeon confesses her feelings, and they officially start dating. Meanwhile, Dae-young struggles with his relationship with army surgeon Yoon Myung-ju, the daughter of their superior, due to military fraternization rules. After returning to Korea, Si-jin and Dae-young disappear during a classified mission and are presumed dead. Mo-yeon mourns Si-jin but later reunites with him in Albania, where she is volunteering. Si-jin reveals they were rescued by a North Korean soldier he had previously helped. The story ends with Si-jin and Mo-yeon, along with Dae-young and Myung-ju, happily reunited.