Doctor Tolson, who is both gifted and capable, experienced the uncertainty of life and the cruelty of the system in a great disaster 20 years ago! In this accident, he lost his beloved girlfriend and his spiritual mentor who was like a family member. After that, he left the hospital system that disappointed him and hid in a small clinic in his own way, becoming a medical delivery man, rescuing emergency patients, fighting for every second and unwilling to give up a ray of hope. He also healed his inner trauma and guilt through the process of going out and saving lives again and again. At the same time, To Lok-sang and the deputy director of the local comprehensive hospital, Li Zhihao, are in a fierce confrontation between enemies and friends. In addition, the tough but soft-hearted female doctor Xu Min'an always intervenes at critical moments. A series of different medical incidents have occurred. Faced with various human relationships between doctors and patients, values between colleagues and self-emotional identification, To Lok-sang realizes that he must return to the system in order to truly reform it. However, this decision has also become the secret detonator hidden in the truth of the catastrophe 20 years ago...