First-year resident Kang Jae-in (Hwang Jung-eum) comes from a rich family that owns hospitals, but she just simply wants to be a doctor who can support herself and help others.

Both Min-woo and Jae-in work in ER under the guidance of Choi In-hyuk (Lee Sung-min), a famously astute workaholic surgeon who puts his patients before himself.

[11][12] The character of trauma specialist Choi In-hyuk was based on real-life doctor Lee Guk-jong,[13][14] who became famous in 2011 when he saved the life of Captain Seok Hae-kyun after Seok received multiple gunshot wounds during a rescue mission from Somali pirates.

The series, which had been struggling at the bottom for its first two weeks with single-digit ratings, made this leap as the former chart-topper The Chaser and runner-up Big wrapped up their runs.

[17] With average ratings of 13.3-15.5 percent, it thereafter topped its timeslot for ten consecutive weeks, despite the rival channels' London Olympics 2012 coverage and the premieres of Faith and Haeundae Lovers.