Lee Hae-sung (Kim Young-kwang) is a surgeon who is transferred from one of the best hospitals in Seoul to a rundown hospital with no ER. After disobeying his previous hospital director, Park Gun (Lee Geung-young), he then meets Jung Ddol-mi (Jung So-min), an orthopedic resident from Busan who came to Seoul to transfer a patient. Ddol-mi tries to meet professor Han Woo-jin (Ha Seok-jin), a cold robotics surgeon who works in Hae-seong's old hospital who saved her life when she was younger before going back to Busan. However, she is stuck in Seoul after trying to save a patient. Meanwhile, a sinkhole appears in Seoul followed by a big earthquake that blocks all access to the city, causing phones, electricity, and water to not function. Hae-seong teams up with Ddol-mi to treat people, but soon medicine starts to run out.