Over the radio, Leanne and Jesse talk a young girl through how to use the supplies on board a small plane to build a makeshift defibrillator when her mom, the pilot, loses consciousness mid-flight. Also, Rox and Willis are taken hostage at gunpoint while on their way to meet the plane at the landing site.

Willis and Rox are called to the scene of a wildfire in the mountains of Los Angeles to tend to the injured firefighters, and they choose to stay to look for a missing young boy who was separated from his father in the chaos.

Rox decides to make amends with her former step coach when she arrives to Angels Memorial with the local high school step team after a pyramid stunt goes wrong. Also, Noa pleads with Leanne and Campbell to try any other method before performing an emergency hysterectomy on a young teenage girl, who is experiencing complications after giving birth.

Mario joins Rox and Willis on the scene of a boat crash and, in Center Stage, Leanne works to save a brother and sister who drank boiling water through a straw as part of a challenge. Also, Max's father tells Leanne to keep Ariel away from his son after he finds them kissing.

Max is brought to Angels Memorial with breathing difficulty, and Ariel tells him she loves him. Also, Rox accompanies Willis and Martin to the funeral of an army buddy of Willis' brother, and Willis decides to get to the bottom of what happened to his brother's unit.

Elliot fears the worst after hearing the emotional testimony by Detective Gomez's wife at his malpractice trial, but he hopes footage Diego shot for his documentary will change her mind. Also, Rox attempts to connect with Willis but he pushes her away, and Leanne attempts to comfort Ariel in the wake of a devastating loss.

While rescuing an injured firefighter, Rox is hit by a drunk driver and rushed to Angels Memorial. Willis begins to realize his feelings for Rox and goes to great lengths to help her. Also, Leanne is excited to tell Ariel good news about her adoption.

Four new first-year residents are immediately put to work by the ER's tough-minded residency director Dr. Leanne Rorish.

Christa has to try and ignore her personal feelings as she and Grace attempt to help a patient who says he was abused at a camp for troubled teenagers.

Willis and Rox arrive at a road rage accident resulting in multiple serious injuries. Also, Elliot doubts his ability as a doctor when he’s sued for his role in the death of the SWAT officer involved in the drug bust-turned-shootout, and Leanne discovers Ariel on an ice cream “date” with Max, a young patient at the hospital.

Angus utilizes his background in psychology when a woman cannot remember how she injured herself and others; Christa bonds with the mother of a patient with cystic fibrosis.

Leanne visits a prison to finally confront the drunk driver who killed her family. Meanwhile, Malaya begins to feel uncomfortable around her patient.

Christa saves a woman's life and then pleads with Neal to perform a surgery that will save the patient's reproductive future. Meanwhile, Mario gets into a fight with a patient after he delivers a diagnosis that could end the man's hockey career.

Angus' older brother, an "all-star" ER doctor, tries to secure a position at Angels Memorial. Meanwhile, Christa's romantic feelings towards Neal begin to grow; and Malaya deals with a patient who is obsessed with her.

Christa is feeling insecure after Neal's former girlfriend makes a return to the hospital after a year of volunteering in Haiti.

Willis defies Campbell’s orders when he helps Mario and Heather perform a radical procedure on a maintenance worker stuck under a boiler that exploded. Also, Angus’ father, Dr. Desmond Leighton, tries to seize Power of Attorney over Mike, who is still in a coma, even though Mike granted that right to his brother, Angus.

The doctors must race to save a girl caught in the crossfire of a shoot-out; Willis shifts his focus to field medicine, choosing to work primarily on an ambulance with his new partner, paramedic Rox; Leanne begins her journey to adopt Ariel.

Angus and Mario treat a patient who is a self-proclaimed psychic and envisions the staff singing and dancing, seeing beauty amid the chaos at Angels Memorial. Also, Willis and Rox put their lives in danger to rescue a congressman and his staffer from a multi-car accident.

The new residents are introduced to the ER. A new doctor from the army who knows many advanced procedures is flown to a shark attack on the beach with Mike Leighton and Leighton falls 20 feet from the helicopter. Dr. Guthrie Jr. is promoted to the director of the ER in addition to the OR.

The doctors treat cult members who unwillingly survived a mass suicide attempt, and Mario decides to connect with his late father’s girlfriend.

The Angels Memorial doctors treat victims caught in a landslide, and a group of children come in from a camping trip with measles putting the entire ER at risk.

Leanne must deal with the difficult decision of whether to save Tom Moreno (Michael Trucco), the police officer who helped her during her family's accident, or his shooter, who has more serious injuries. Also, when Malaya's pregnant ex-girlfriend, Carla Niven (Shiri Appleby), arrives at the hospital with pain in her arm, Malaya is shocked by her MRI results.

Willis and Campbell are sent to a Russian submarine in U.S. waters to treat a sailor badly wounded during an explosion, and violent convicts injured during a prison riot descend upon Angels Memorial.

Leanne defies Campbell's order and uses the hospital helicopter to reunite a family for the last time. Meanwhile, Willis and Loa use a cell phone app to communicate with an autistic young girl.

After pulling a double shift, Mario risks his own life when he follows Willis to a construction site where two brothers are trapped on a crane 300 feet above the ground.