A blackout at Chastain Memorial Hospital requires the staff to treat their patients without the help of any technology. Bell orders the staff to stop accepting new patients and transfer those on life support, but when a child in need is rushed to the ER, Conrad and Devon go against the mandate. Meanwhile, Mina and Austin are tasked with performing heart surgery on a premature baby, despite the lack of power, and Nic works tirelessly to organize the staff and patients who stay during the blackout.
Bell grows frustrated when Marshall Winthrop, Conrad’s dad and new chairman of the board, requests Conrad’s input in his discussions about the hospital’s expenses. As Conrad and Nic work to cut costs for their patients in need, Julian Lynn, a sharp and sophisticated medical device rep, meets the staff at Chastain and inserts herself into the ongoing work of the doctors to promote her costly products.
Nic and Conrad contemplate their past when they team up to diagnose a happy husband and wife who are both admitted to the hospital with mysterious symptoms. Bell and Marshall butt heads on a work trip when their cut-throat business tactics don’t align.
Chastain is flooded with concert goers when a stampede at a music festival grounds leaves many in need of doctors. As Conrad and Nic race to help Josh Robinson, a professional adventure guide with a long list of prior injuries, Devon works with a musician who swears he is sober, even though his toxicology report suggests otherwise. Meanwhile, Bell stirs the pot when the hospital’s revered orthopedic surgeon, Dr. Kit Voss, demands a better resident, Julian works to get her boss on Bell’s good side and Winthrop continues to push Conrad to believe he’s a changed man.
When Bell makes the executive call to utilize Julian Booth's medical devices, rather than the hospital's usual products, Kit and AJ must stop their momentary feuding in order to team up against him. Elsewhere in the hospital, Conrad and Nic work to make a child's dreams come true after finding out his cancer has returned and the rest of the staff takes notice of Julian and Devon's new friendship.
Halloween at Chastain proves to be just as spooky as ever when Conrad is tasked with diagnosing a young woman admitted to the hospital with extreme night terrors. Meanwhile, Devon faces his first Halloween in the ER, Nic panics over her decision to bring her newly sober sister to Mina's epic annual Halloween party and Bell finds an interesting way to make use of his new assistant.
When patients from the hospital's prescription drug trial start suffering life threatening side effects, Nic fears that her sister Jessie may be in danger. As a result, she and Conrad work to convince Bell that these trials are not worth the risk. Meanwhile, Mina, Austin and Kit must set aside their competitive nature and work together on a patient whose health is quickly deteriorating and Devon uses Julian as the beta tester for a product he's designed.
Conrad goes head-to-head with Bell after he recommends one of Julian's risky medical devices to Zoey, who's already lost one son and is back in the hospital with the other. Nic fears that Conrad may be getting overly attached to his patient. Meanwhile, Mina and Austin grow closer while working on a difficult heart transplant, Devon embarks on a very difficult day and Dr. Lane Hunter returns.
Devon's doubts about his relationship reach a peak as his friends and family gather for his big wedding day. As Chastain's leading medical device company, Quovadis, continues to succeed, Julian (guest star Jenna Dewan) makes a discovery that leaves her uneasy about her involvement in it all. Meanwhile, Conrad continues to work on his relationship with Marshall and Bell takes a risky offer in order to make a mistake from his past disappear.
