Dr. Shaun Murphy, Dr. Audrey Lim and Dr. Claire Brown's E.R. patient is forced to reveal a secret to her husband after their treatment caused a complication. Meanwhile, Dr. Neil Melendez, Dr. Morgan Reznick and Dr. Alex Park struggle with a patient whose parents don't believe in vaccinations.

Dr. Shaun Murphy and Dr. Alex Park treat two patients who collapse at the local airport and whose symptoms point to an infection that may become airborne. The staff races to contain the infection before it spreads to the rest of the patients in the ER, resulting in a hospital quarantine during the holidays.