While taking their vacation, Si Jin and Dae Young catches a thief on a motorcycle. Si Jin happens to meet Mo Yeon at a hospital where the thief is admitted. For some reason, Si Jin's heart is pounding as he meets her.

After engaging in a perilous operation in Afghanistan, Si Jin comes back and meets Mo Yeon for the second time.

Si Jin and the Alpha Team get off the transport plane and march to the medical team with the sun on their backs. Si Jin recognizes Mo Yeon instantly but passes by. They find their hearts pounding; is it due to discomfort or butterflies in their stomach?

With guns pointed everywhere in a highly-charged Medi Cube, Mo Yeon cannot make up her mind. Meanwhile, Dae Young and Myung Ju run into each other at Urk airport. He can hardly bring himself to move; and she approaches him one step at a time.

After her first kiss with Si Jin, Mo Yeon is confused: is this anxiety or excitement? Meanwhile, Si Jin receives a call from her. On the other end, he hears her voice mixed with tears, asking him to save her. He hurriedly drives his car in search of her.

A powerful earthquake strikes Urk. The earth shakes like waves, villages disappear and mountains collapse. The medical team and the soldiers run into the rescue scene, which is a complete pandemonium. Everyone struggles desperately in the disaster.

At a rescue site where a momentary decision and choice means a matter of life and death, Si Jin and Mo Yeon face a crisis. What choices will they make? Will they be able to rescue everyone?

Both the medical and the military team for the rescue mission finally find survivors and start working on rescuing them. Meanwhile, the ground shakes and the seismograph starts to show a suspicious movement.

Mo Yeon's will gets announced through the speakers. Mo Yeon tries to avoid Si Jin out of embarrassment. However, Si Jin never loses track of her. Meanwhile, Lieutenant General Yoon suddenly visits Urk, making all four of them nervous.

Mo Yeon is torn between the decisions she has to make as a doctor. Dae Young thinks about his future after seeing Argus, who has turned into a criminal. Packages arrive from Korea, and Mo Yeon and Young Ju notice a weird package for Si Jin and Dae Young.

Dae Young and Myung Ju are under quarantine, and Medi Cube is designated as the base medical facility for treating the virus. Everyone works hard to fight the epidemic but an ominous shadow blocks the truck carrying the much needed medical supplies.

Deep in the night, Si Jin enters Agus' hideout. Loud gunshots are heard from within! Dae Young becomes aware of Si Jin's solo operation and is seized with bad presentiments… Mo Yeon finally meets Si Jin but she faces an unexpected situation.

The medical staff come back to their daily lives but they feel somewhat empty due to the memories at Urk. Mo Yeon throws her resignation letter at the chairman's face upon her return. Si Jin, Dae Young and Myung Ju receive orders to return to Korea.

Mo Yeon rushes to treat the patient that has just arrived in the ambulance. As the door opens, before her eyes is Si Jin, unconscious and completely covered in blood. No matter how hard she does CPR on him, his vitals just keep getting weaker and weaker.

Si Jin and Mo Yeon spend many happy days together. However, there is no end to the strife between Dae Young and Myung Ju. The Alpha Team gets sent on a long-term operation to fight a battle that can't be lost; and Mo Yeon feels insecure about it.

Si Jin, Mo Yeon, Dae Young and Myung Ju have all come to the end of a very long separation. However, can they continue to live their daily lives happily ever after?