Prepare for a dramatic overhaul in the emergency department of Gaffney Chicago Medical Center as “Chicago Med” enters its highly anticipated 10th season. The long-running NBC medical drama is set to introduce two compelling new series regulars, Sarah Ramos and Darren Barnet, both 33, while simultaneously bidding farewell to a significant character, signaling a major casting shake-up that will undoubtedly reshape the hospital’s dynamics and storylines.

When “Chicago Med” returns on Wednesday, September 25th, viewers will meet the formidable Dr. Caitlin Lenox, portrayed by Sarah Ramos. Described by a source for Deadline as “an ED Attending poised to get Gaffney Medical into shape,” Dr. Lenox sounds like a no-nonsense addition, likely bringing a fresh, perhaps challenging, perspective to the emergency room’s operations. Her arrival suggests a new era of efficiency or perhaps a clash with existing leadership and practices. Reports indicate that Dr. Lenox, an Army veteran, will become the new co-head of the ED, and eventually the outright Chief of Emergency Medicine. She’s characterized as fearless, measured, and rational, with a surprising, sincere, and creative compassion when it surfaces. This hints at a complex character who will undoubtedly leave her mark on Gaffney.

Joining her is Dr. John Frost, played by Darren Barnet. Frost’s character immediately sparks intrigue, as he’s revealed to be “a pediatric resident who is harboring a secret.” This tantalizing detail promises a mysterious and potentially emotional backstory, offering fertile ground for character-driven narratives as the season unfolds. Further details reveal Frost was a former teen heartthrob from a popular television series who joined Gaffney after his previous hospital closed. His dedication to his young patients often goes beyond just medical treatment, stemming from a troubling childhood experience involving his parents taking advantage of his fame and wealth, leaving him in medical debt. This deep backstory suggests he’ll have strong opinions, particularly regarding child abuse and parental deception.

These exciting new additions come on the heels of a significant departure. In June, PEOPLE confirmed that Dominic Rains, who has played the charismatic and often troubled Dr. Crockett Marcel for five seasons, would be leaving “Chicago Med.” Marcel’s exit was subtly set up in the Season 9 finale, where he was profoundly affected by the death of a young patient whose liver transplant he had to cancel, followed by the boy’s father dying by suicide out of grief. This dual tragedy deeply resonated with Marcel, stirring up painful memories of losing his own infant daughter to leukemia. Sharon Goodwin advised him to take time off to cope, and it’s implied that he chose not to return, seeking a fresh start in Boston. This marks a major loss for the series, as Dr. Marcel had become a central figure and a fan favorite, deeply involved in pivotal patient care stories and evolving from a “sleazy womanizer” to a compassionate surgeon.

While some beloved characters are departing, several key figures are confirmed to return, ensuring a blend of fresh narratives and familiar faces. Jessy Schram (Dr. Hannah Asher), Steven Weber (Dr. Dean Archer), and Luke Mitchell (Dr. Mitch Ripley) are all expected to reprise their roles. They will be joined by original cast members Oliver Platt (Dr. Daniel Charles), S. Epatha Merkerson (Sharon Goodwin), and Marlyne Barrett (Maggie Lockwood), providing a strong foundation for the new season.

Adding to the behind-the-scenes transformations, long-time co-showrunners Diane Frolov and Andy Schneider have stepped down after nine years, with Allen MacDonald taking over as the new head writer. This change in creative leadership signals a deliberate effort to inject fresh energy and direction into the series, aligning with Marlyne Barrett’s earlier remarks about Season 10 feeling like a “second coming.”

These shifts in “Chicago Med” are part of a broader pattern of change across the entire “One Chicago” franchise over the past year. “Chicago Fire” saw the departure of Eamonn Walker (Chief Wallace Boden) as a series regular in its Season 12 finale, following earlier exits from Alberto Rosende (Blake Gallo) in December 2023 and Kara Killmer (Sylvie Brett) in February. Similarly, “Chicago P.D.” bid farewell to Tracy Spiridakos (Detective Hailey Upton), who had been a pivotal character since 2017, after its Season 11 finale in May.

These interconnected changes across the “One Chicago” universe indicate a deliberate strategy to refresh storylines and introduce new character arcs, ensuring that each series remains dynamic and engaging for its audience. For “Chicago Med,” the arrival of Dr. Lenox and Dr. Frost, coupled with the emotional void left by Dr. Marcel, promises a season rich in medical emergencies, personal struggles, and intriguing new mysteries. Get ready to be on the edge of your seat when “Chicago Med” returns on Wednesday, September 25th, at 8 p.m. ET on NBC, as the Gaffney Chicago Medical Center embarks on its most transformative chapter yet.