Season synopsis
Contains spoilers for this season and earlier seasons.
A fireworks display at an anti-war rally sparks a panic and stampede. Neela is trampled and critically injured, but surgery succeeds and she recovers. New chief Kevin Moretti imposes strict procedures while County handles the casualties. Luka remains in Croatia as his father’s health declines; his father dies later in the season, and Luka and Abby then plan a trip there together. With Luka away and Joe’s nanny caring for him, Abby feels increasingly isolated.
Joe’s fall from a playground structure deepens Abby’s distress. She returns to drinking, hides it from colleagues and spirals during a blackout, where she has a drunken one-night stand with Moretti. Luka returns early from Croatia, and Abby’s guilt worsens. She enters rehab, checks out and returns to the ER; later, preparing to join Luka in Croatia, she confides the affair to her sponsor. She tells Luka about both her drinking and infidelity. They confront the damage to their marriage rather than treating the relapse as settled simply because she has resumed work.
Abby travels to Croatia to reunite with Luka and Joe, while County continues through leadership changes and Pratt is passed over for chief. Moretti eventually returns and tries to make amends with Abby and Luka. In the finale, a drunken patient puts the hospital in danger and Luka decides to forgive Abby after an encounter with Moretti. The closing cliffhanger is an ambulance exploding, with Sam or Pratt possibly inside; the season does not resolve which person is there or whether anyone survives.