As Angels Memorial Hospital welcomes its new wave of residents, they quickly get drawn into the reality of what working in the US's busiest ER is like, as Dr. Leanne Rorish makes use of the extra hands to deal with an influx of patients.
Christa fights for her patient when the woman's reproductive future is jeopardized, and only Neal can help her. When Mario delivers upsetting news to a hockey player who landed in the ER, his diagnosis is met with an unexpected reaction.
The doctors of Angels Memorial are pushed to the brink after they endure 36 hours of Code Black. Mario lands Angus in trouble after he pushes him to perform surgery before washing his hands off the matter when they get discovered.
Christa's newest infant patient forces her to confront painful memories. Dr. Guthrie's son joins the staff at Angels Memorial, shaking things up as tension rises between him and Leanne.
Neal's familial issues come to light in the hospital after his mother is brought in for treatment. As her mysterious symptoms cause a quarantine, tensions rise between Neal and his father, an acclaimed neurosurgeon.
Leanne faces a dilemma when she has to choose between treating a police officer whom she personally knows, and treating the man who shot him. A face from Malaya's past arrives at the hospital with a shocking diagnosis.
The hospital receives an influx of patients when a car ran into pedestrians at a street fair, but as the doctors race to save the injured, Angus tries to help the driver regain her memory to figure out what happened.
Malaya tries to help her former girlfriend beat cancer, even if the help is unappreciated. Christa faces tremendous pressure when she is left to cover all emergencies outside the ER.
The staff faces a harrowing case when an injured family is rushed to the ER in the wake of a home invasion. The lead actor of the Lion King musical tour arrives at Angels, but Leanne does not have good news for him.
As the ER gets a new department head, Leanne is pushed to the end of her tether when Jesse's life hangs in the balance following a heart attack. Mario goes against Neal and embarks on a journey to find a patient's son.
The doctors head out into the field to help with a multi-car crash. But as they make difficult decisions about who they could save, two of them find themselves in a perilous position due to a man's desperation to save his wife.
With three doctors missing, Neal and Leanne have to deal with the consequences of their decisions in the field. Malaya rushes to Carla's side as the latter goes into labor.
Leanne makes a shocking decision about her career. Angus struggles to adjust when his talented brother prepares to take a position at Angels. Christa and Neal grow close.
A patient's obsession with Malaya leads to tragic consequences for the staff. Leanne confronts her painful past and makes an attempt to heal and move on.
With a dangerous man loose in the hospital, the staff scrambles to save Gina. Angus desperately looks for Malaya who ends up in peril when Gordon refuses to take no for an answer.
The arrival of Neal's ex sends Christa into a spin. An NFL star tries to convince his high school coach to agree to a surgery that could save his life.
Angus deals with the consequences of his actions with Gordon. Christa and Grace put their differences aside to help an abused teenager.
Leanne tries to resolve the situation with the nurses who are threatening a strike. The fallout of Angus's addiction implicates Heather. The staff at Angels work under pressure when they receive the injured of an explosion at a presidential campaign.